The London Assembly slammed anti-union mayor Boris Johnson yesterday for threatening to “lock out” striking firefighters, branding his plan a threat to public safety.

The Tory London mayor — who has overseen scores of fire station closures — asked his fire commissioner to investigate “withholding payment from firefighters for part or the whole period of duty on which they are on strike.”

A motion passed at a meeting of the assembly, with support from Labour, Green and Liberal Democrat members, urged the mayor to row back on his “deliberately antagonistic approach.” 

It warned that “the safety of Londoners will be jeopardised” in the event of a lock-out.

Labour’s Fiona Twycross, who tabled the motion, said: “This a narrow-minded, politically motivated decision from the mayor. 

“What is worse, locking firefighters out like this will pose a genuine risk to the safety of Londoners.

“Evidence from similar cases in Buckinghamshire, Essex and Surrey tell us that lockouts like this don’t work, but the mayor is intent on provoking firefighters and ramping up the dispute.”

The row comes amid a bitter dispute over pensions and retirement age which has seen the FBU stage a series of two-hour walkouts over eight days. 

Most fire authorities — including London — paid firefighters for working the remainder of their shifts.

But the union slammed Buckinghamshire’s “lunatic” chief fire officer Mark Jones for branding strikes “partial performance” — for which he docked a whole shift’s pay.

FBU London regional secretary Paul Embery warned yesterday the dispute would escalate if Mr Johnson extended union-busting practices to the capital.

He told the Star: “Boris Johnson can investigate all he likes, but our position is clear.

“If he goes ahead there’ll be a huge reaction from our members — in London and nationwide.

“It will only deepen the dispute, and firefighters will challenge it in whatever way they can.”

Mr Johnson said the motion’s contents were “silly” and he would not take action that would pose risk to Londoners. 

His press officers declined to comment further when contacted by the Star.