The town halls’ borough-wide 20mph speed limit, costing almost £500,000, has been branded “toothless” with not a single ticket issued in more than six months since the ban started.

In October, Islington Council’s ruling executive voted through a £423,000 plan to make the 25 main roads under its control, such as Blackstock Road and Caledonian Road, subject to the limit – residential roads have been subject to the limit since.

Only TfL maintained roads like Seven Sisters Road are still 30mph, but an investigation by the Gazette shows that neither the police, not the council has issued any penalties for motorists driving between 20 and 30mph.

Cllr Terry Stacy, leader of the opposition Lib Dem group, said: “Islington Council were quick to enjoy all the plaudits when they announced it, but it’s a completely toothless policy.

“The 20mph speed limit is a good idea, but the difference is we [the Lib Dems] would enforce it.”

When the council announced the speed limit, Scotland Yard’s traffic management unit wrote to them saying “an unrealistically low speed limit in these roads will create an enforcement problem where one does not currently exist. We will not routinely enforce 20mph speed limits and zones”.

Cllr Stacy said: “We would put huge pressure on the police and if they wouldn’t do it we would do it ourselves.

“Where residents have raised concerns the council should be looking to address them, not passing the buck to the police.

“They were quite ready to get the credit for it, but not doing the hard work. They are only interested in the good publicity.”

Cllr Paul Convery, Islington Council’s executive member for community safety, said: “We want to make Islington’s roads safer for all – that’s why we have chosen to introduce a 20mph borough-wide limit, which we hope will shift the culture in Islington toward lower speeds.

“Signs are very visible on the entry roads into the borough and along major routes to remind drivers of the limit.

He added: “Speeding is a criminal offence and only the police have the powers to enforce the speed limits on our streets. We will continue to work with them and press on them the importance of supporting 20mph in addition to pressing for new legislation so that we can directly affect speed compliance.”

Hackney Council has been the second borough to commit to a 20mph limit, which came into force at the end of March.