A colony of snakes living by the Regent’s Canal - which can grow up to two-metres long and squeeze cats and small dogs to death – have been placed on a list of invasive species.

Aesculapian snakes are listed in the Wildlife and Countryside Act 1981 - meaning it is illegal to allow the species to spread or escape into the wild – and the government advisory quango, the London Invasive Species Initiative (LISI) have labelled them a “non-native species of high concern”.

However there are over 30 of them living in Camden, and the fear is they could spread further down the canal into Islington and Hackney.

LISI has placed the species – which is thought to have originally escaped from London zoo - in its second highest-priority group, along with the American mink, which escaped from fur farms in the 50s, the goldfish, the Italian crested newt and the Rhododendron.

The snakes are native to Central Europe and the concern is that species introduced into foreign eco-systems, where they have no natural predators, can spread rapidly and displace indigenous species - like the American grey squirrel which has wiped out the British red squirrel population.

Aesculupians, which can also kill rats and birds by constricting them, usually find their homes along river beds or streams - making Regent’s Canal the perfect home for them.

In recent weeks there have been several reported sightings of them up trees, on rooftops and climbing up drains in North London.

The LISI list, which is updated quarterly, has called for research into monitoring the snakes’ ecology, their breeding sites and methods of removal.

LISI manager, Karen Harper, denied the group has any plans to cull the colony however, saying the snakes have been in Camden for a long time and as far as they are aware has not yet moved further downstream.

‘The species of concern list for the Greater London area has been compiled by a range of industry professionals and land managers within London,” she said.

“At present there is limited information on what effects the species may have on our local ecosystems and further information would be hugely valuable in developing appropriate management plans for this population.”

She continued: “With so many other invasive non-native species having a detrimental effect on our environment, it is not feasible to spend limited resources on a species that does not at present seem to be having a significant impact on our ecosystems.

“As for the concern about people’s safety, when left alone Aesculapian snakes are a docile and non-venomous species - please rest assured that your children will not risk being crushed by snakes whilst wandering through central London.”

Ian Shacklock, co-ordinator of the Friends of Regent’s Canal, said the initial feedback from his group is not to interfere without the full facts.

“The snakes could be a good thing for the canal if they are gobbling up rats,” he said.

“The thing that puts parents off their children canoeing and kayaking in the canal is Weil’s disease, which is spread by rats.”

A colony of the animals has lived for several decades in north Wales after they escaped from the Welsh Mountain Zoo.