London may be in the grip of a housing crisis, but it has more than 67,000 homes with no permanent residents, according to government figures.

Last year in the capital there were 22,481 long-term empty homes - long-term being more than six months - and 44,641 second homes.

At the same time, rough sleeping figures are at a record high and London councils have more than 56,000 families and 88,000 children living in largely unsuitable temporary accommodation.

More than 21,000 of those households are outside of their home borough and some, as revealed in the Children's Commissioner's Bleak Houses report last week, are living in shipping containers.

Islington charity Action on Empty Homes blames buy-to-leave investors for the empty homes, while the figures for second homes - which are not legally defined - are thought to contain a mix of genuine second homes, AirBnB-type properties and empty homes avoiding a council tax premium.

Labour leader and Islington North MP Jeremy Corbyn told this newspaper: "While social housing waiting lists grow and first time buyers struggle to get on the ladder it is offensive to learn there are just under 23,000 properties in London sitting empty for more than six months.

"The housing crisis is caused by the few who use houses as investment opportunities. This influx of large sums of money has seen prices sky rocket for ordinary people.

"Houses are homes, not assets. We need to clamp down on buy-to-leave by charging a levy on second homes and strengthening councils powers over empty properties, as well as building one million genuinely affordable homes."

As expected, inner London has a higher percentage of both empty and second homes than the outer boroughs.

Southwark has the most empties - and the highest increase - with 1,766, up 57 per cent from 1,128 in 2017.

Second homes figures vary massively, with Kensington and Chelsea having the most at 8,854, followed by Camden with 7,122 and Tower Hamlets with 6,160. Hackney has 734, Southwark has 497 and Islington has 301.

The stats were published by the Ministry of Housing, Communities and Local Government (MHCLG) based on council tax data.

Camden also has the third most empties at 1,210. That means one in every 13 of the 109,496 homes in the borough is not housing anyone permanently.

These figures do not include homes that have been empty for less than six months, so new developments are not counted.

This year the government responded to years of lobbying by councils and doubled the council tax premium they could charge to 100pc for homes left empty for two years. But that leads some landlords to avoid the premium by claiming their property as a second home.

It's something housing officers across the country are trying to stamp out, and relief for second homes has now been scrapped by almost all local authorities.

Chris Bailey, campaigns manager at Action on Empty Homes - whose annual report on the issue will be published next month - said: "Some people have multiple second homes all in the same borough. All appear to be empty and they are just hoarding properties to increase value.

"One officer I know does the 'staying overnight and making a cup of tea test'. She won't accept it's a second home if it doesn't pass. Because a lot of homes don't have electricity.

"Obviously some are real, like in Cornwall. But Newcastle has 2,500, Leeds 2,000 and Bradford almost 2,000. These aren't holiday destinations."

Councils differ in their definitions of a second home. Camden explains its huge number by saying it includes empty rental properties, guardianships and AirBnBs - of which there are 74,000 in London, almost 50,000 of which are whole homes.

Haringey recorded zero empty homes, because since scrapping relief it no longer feels the need to categorise them.

Chris says both are far from ideal practices.

"It's simply not responsible to stop counting second homes," he said. "Policy-makers and the government need to understand how housing stock is used or they can't assess how granting planning permission or other housing policy is likely to impact on our housing crisis.

"They should be able to set planning controls on whether it's a primary residence or not. It's our view that for a home to be called a residential property it needs to have permanent residents.

"This takes us to the debate about 'buy to leave' in London and so-called 'ghost towers'. Many Londoners are now asking why we don't make sure we are actually building homes rather than just more wealth stores and tourist lets. What we would like to see is a national landlord register and property use register."

At local level Hackney Council is leading the way in tackling buy-to-leave landlords, though it still has 933 empties. Its in-house firm Hackney Sales only markets the private-sale homes locally and not to overseas investors or buy-to-leave landlords.

It also restricts developers it works with, for example its private homes on Hoxton's redeveloped Colville Estate were sold locally, and almost all private sales on its flagship Kings Crescent Estate development in Green Lanes were sold to "owner occupiers", with none going overseas.

A Hackney spokesperson said: "Every home that sits empty is an insult to our more than 3,000 families living in hostels, bed and breakfasts or other temporary accommodation.

"We want to lead by example in preventing homes being left empty. By marketing the outright sale homes to local people first, we're showing how new developments can provide places for people to live in rather than investment opportunities."

Hackney, which has north of 3,000 families in temporary homes and a waiting list of 13,000 plus, also has a new initiative encouraging owners of empty properties to let them out to the council to use as temporary accommodation by helping foot the bill for repairs.

Islington Council introduced a supplementary planning document (SPD) in 2015 allowing it to take landlords to court if their homes are left empty for three months.

It relies on electoral roll data and reports from neighbours, but there are only 18 less empties now than when the policy was introduced and the council wants the government to do more.

Housing director Maxine Holdsworth said: "Without extensive legislative reform we are limited in our ability to prevent 'buy-to-leave' investors using desperately needed homes as idle chips in their investment portfolios."

Southwark's housing director Michael Scorer said there were a "number of reasons" why it had the most empty homes in London, including blocks being cleared out ahead of redevelopment.

He added: "The council encourages property owners to bring their homes back into use and has done what it can within its power to make it less attractive to keep an empty second home here."

Camden said it takes the issue of empty homes "very seriously". Its Better Homes chief Cllr Meric Apak said: "There are a number of empty privately owned properties undergoing renovations, and a number of new builds waiting to be sold or rented.

"Camden places levies on homes that remain empty long term, and it is looking to increase those in an attempt to reduce the number of long term empty cases within the borough."

Haringey leader Cllr Joseph Ejiofor said tackling the housing crisis was a "top priority", which is why it had doubled the council tax premium and scrapped discounts for second homes.

Ealing, with its 850 empty homes and 200 second homes, was one of the places singled out by the Children's Commissioner's report for housing families in converted containers.

Stories of families stuck in temporary accommodation were highlighted in the Hackney Gazette's award-winning Hidden Homeless campaign, and remain on the local news agenda.

Last week a domestic abuse survivor was given a last-minute reprieve by Hackney Council after being told to choose between moving to Stoke or becoming homeless.

And in Camden the Happy Vale Hotel hostel, whose squalid conditions the Ham&High revealed during an investigation last year, was closed and put up for sale in February after its owners were taken to court by the council.

Yet the lack of homes and rising rents mean national spend on temporary accommodation was not far off £1billion last year. Newham Council, which had more than 5,000 families in temporary homes as of September, spent the most at £61.1m, with Hackney, Enfield and Westminster also spending £54.8m, £49.9m and £48m respectively.

The huge numbers have led to new mega hostels being built in place of permanent housing.

Sadiq Khan's deputy mayor for housing James Murray, who was Islington's housing chief when it brought in the SPD, said: "It is a scandal that any homes are left empty in the middle of London's housing crisis.

"Sadiq has changed City Hall's planning policy to support mechanisms like the one Islington brought in, and he has asked ministers to allow councils to charge an unlimited levy on homes that are left empty.

"Those are the kind of powers we need to end the shame of homes standing empty as people sleep rough on the streets outside."

The UK as a whole has 216,000 empty homes and with short term empties that rises to 634,000. There are also 252,000 second homes, meaning more than 900,000 homes have no one living in them.

Chris said: "We have a housing crisis. We have 1.1million people on the social housing list and 87,000 families in temporary accommodation - 120,000 children growing up in unsuitable places.

"It is simply not acceptable to have 216,000 long-term empty homes in the country.

"And there are 252,000 second homes. While some are undoubtedly real, we believe a lot of them in urban areas are being used to reap lucrative profits on AirBnB or simply as a form of investment."

MHCLG did not respond to a request for comment.