Campaigners against the CS11 cycle superhighway are seeking legal advice for a judicial review against the Swiss Cottage Gyratory part of the route.

Jessica Learmond-Criqui, who is heading up a group against the development, said they were in the process of taking “comprehensive legal advice”.

She and her fellow protesters also claim road chiefs at Transport for London (TfL) are going ahead with the scheme without looking at the impact on roads around Swiss Cottage.

And they say TfL hasn’t done a cost and benefit analysis of the project.

Jessica also has concerns the work will start without the agreement of Camden and Westminster’s councils, or the Royal Parks. The route runs through both of the boroughs as it makes its way from Swiss Cottage to the West End.

She and the group believe the reworking of the gyratory will lead to gridlock and increased pollution in Hampstead, Belsize, West Hampstead, St John’s Wood and the surrounding areas.

Andrea Taylor, headteacher at Hampstead Hill School, said: ”We are campaigning against this unnecessary and futile new gyratory scheme because it will affect parents delivering and collecting their children who will have to breathe in fumes from an extra 300 to 475 vehicles an hour on our closest and busiest roads as predicted by TfL.”

And she claimed: “Toxic fumes will affect children and cyclists who will be impacted by the added pollution and gridlock caused by the new scheme.”

Now Jessica wants Parliament to intervene and challenge the decision.

She said: “The parliamentary transport select committee needs to ask the London mayor and TFL to explain why no impact assessments or cost/benefit analyses have been undertaken before the work commences in July.

“The transport select committee should ask why this Swiss Cottage cycle superhighway is being started without the agreement of Camden and Westminster local authorities and the Royal Parks authority, who have not agreed for the cycle superhighway to be built in their boroughs.”

TfL declined to comment on the campaigners’ accusations.