Conservative leader David Cameron, in Solihull to campaign for the local government elections, has accused ministers of "blackmailing" councils into introducing congestion charging.

Mr Cameron insisted the Government was holding local authorities to ransom by refusing cash from its Transport Innovation Fund (TIF) unless they introduce schemes.

A future Conservative government would free up the funding so local people could decide how to solve their own transport problems, he pledged.

Mr Cameron unveiled a policy paper on local transport during his visit to the West Midlands. He said there was £200 million a year in the TIF budget which councils could only access for congestion charging schemes - amounting to "blackmail".

Mr Cameron said: "If councils want to go down that path (congestion charging) then that's fine, but they should not be made to do it.

"We believe in bottom-up, council-led solutions rather than top-down government blackmail solutions."

Under the plans, Conservatives would honour existing commitments to councils, but then free up funds for locally-devised schemes. The Tories are aiming to turn a run of favourable polls into concrete progress at the ballot box on May 1, as well as making breakthroughs in parts of the North where they have traditionally been weak.

Mr Cameron has already refused to be drawn on whether winning fewer than 100 extra seats would be a poor performance, stressing that the party was starting from a very high base.