Hackney Council has insisted its flagship Kings Crescent Estate development is safe - despite admitting its walls contain the same insulation as some used at Grenfell Tower that has since been banned from use in high-rise buildings.

The council says the new regulations banning Kooltherm K15 from use in high-rise buildings do not apply retrospectively to developments like Kings Crescent that went up before December 2018 - and blames "confusing" advice notes issued by the government for its inability to provide documentation to mortgage lenders regarding one couple's flat there.

The couple, as reported in last week's Gazette, suspected something could be amiss with their Green Lanes building when surveyors valued the £685,000 flat they bought two years ago at £0 until Hackney could prove its compliance with the December 2018 regulations.

For a surveyor to give the flat a higher price and to secure a mortgage at a decent rate the couple needed the council to sign a form stating it met new building regulation guidelines introduced in December. They contacted the Gazette after council officials gave them the run-around for months.

The council now says the insulation used to build the 273 flats opposite Clissold Park is called Kooltherm K15, may be combustible, and is now banned for use in buildings over 18m tall. But the building is safe because of the way the insulation is built into the walls, it is understood.

The Grenfell fire triggered the largest review of safety in the UK since the Second World War, leading the government to introduce a flurry of new building rules.

Kooltherm K15, manufactured by Kingspan, made up about 15 per cent of the Grenfell Tower insulation. A separate Kingspan product, Kooltherm K12, was used in the council's Bridport House development - where tenants were told last month they must evacuate for a year while the material is either painstakingly removed from the wall cavities or entirely demolished. This material, unlike Koolspan K15, was not compliant with rules even at the time of building work.

The risk at Bridport House was only uncovered by surveyors investigating the wonky bricks at the building opposite Hoxton Park in March. Since then fire wardens have been patrolling the building round-the-clock at a cost of £16,000 a week.

But although the council has not carried out any investigations into Kings Crescent, it reassured the Gazette it is certain it is safe.

Mayor of Hackney Phil Glanville said: "The safety of our residents is our top priority and - while I recognise the uncertainty some residents might feel - we want to reassure everyone living on the Kings Crescent estate that their homes are safe, as has been verified by fire risk assessments of all the new buildings.

"While we are confident that these homes are safe, the government's unclear and contradictory advice over the last year about the actions that building owners need to take around safety has led to widespread confusion from landlords, mortgage lenders and the wider public.

"This new requirement by mortgage lenders has taken building owners across the country by surprise, and like other councils, housing associations and developers we are working as quickly as we can to provide the necessary documentation for our leaseholders."

He called for "a root and branch reform of building regulations".

Bridport House is considered a fire risk because of its timber frame. Buildings at Kings Crescent do not have these frames.

Both Bridport House and Kings Crescent were designed by architects firm Karakusevic Carson.

Since we published last week's story about the couple unable to secure a mortgage, a number of people linked to the tenants and residents' association (TRA) have got in touch to say they have had no problem obtaining competitive mortgages even in recent weeks and months.

The mortgage brokers for the couple claim this is the first case of its kind they have come across, where a council was unable to cough up the documents needed.

"After speaking to two of the biggest lenders and a number of large survey companies it is something that's being requested on any properties with some form of cladding, since the new regulations came into place in December last year," they said.

"We were told by these lenders and surveyors that they've not had any problems in getting these certificates from property owners or councils and between them they've had hundreds or even thousands of cases such as this."