Labour county councillors were shot down as they tried to explain Mayor of London Sadiq Khan wanted the Metropolitan Line Extension to go ahead.

Conservative and Liberal Democrat politicians put forward a motion at Hertfordshire County Council’s budget meeting this week to show they still support the project - despite last month’s shock rejection from the TfL.

County councillors supported the motion, which said: “This council is dismayed at the decision of the Mayor of London to withdraw support for the project being led by Transport for London to extend the Metropolitan Line to Watford Junction on the basis that it cannot accept future cost risk.”

However, Hertfordshire Labour county councillors including Cllr Asif Khan and Cllr Nigel Bell did not agree the Mayor of London was to blame.

They added that the Labour group was not told about the motion and so wanted to make an amendment blaming a “breakdown in negotiations between the Mayor of London and the Secretary of State for Transport Chris Grayling”.

Their amendment added there was also “no agreement on the carrying of future cost risk” but other parties rejected their revision.

Cllr Khan, Labour’s transport spokesman, said the party put forward a “balanced, non-partisan amendment to kick start the Met Line extension”.

He said after the meeting: “The amendment was an attempt to raise the issue above petty party politics, but the Liberal Democrats and Conservatives resorted to attacks on the Mayor of London and ended up politicising the issue.

“It seems they have given up on the Met Line extension by the way they acted today, however we will work with the Mayor of London to lobby the Department of Transport to get the project built.”

Liberal Democrat group leader Cllr Stephen Giles-Medhurst said claims the Labour group was not told about the motion were “not true”.

He believes they were trying to “let Mr Khan off the hook” as the Government and other bodies have provided £358 million whereas TfL contributed £49 million.

He said: “I cannot understand what the Mayor of London is playing at. They have already spent £71 million on the project, why not deliver the rest of it?”

Conservative council leader Cllr David Williams, said: “We think it is perfectly reasonable that TfL would stand by their figures but they are unable to accept the risks.”