Conservatives in the London assembly have called on the mayor to scrap his plans to raise the Capital's congestion charge.

Ken Livingstone is currently considering a rise from £5 to £8 in a bid to raise additional cash and cut pollution and traffic jams.

But Tory spokesman on the charge, Angie Bray, branded the rise "preposterous".

"There is a mountain of evidence showing businesses, both large and small, creaking under the lost custom caused by the charge – and that is before this ridiculous increase is even introduced," she said on Tuesday.

Her comments came as the mayor prepares to give evidence on the increase to the assembly's transport committee.

The increase will raise an additional £50 million of revenue, and should prompt "further reductions in congestion", according to the mayor.

Livingstone has said that he is proposing one large increase in this mayoral term "to maintain the effectiveness of the charge" and help fund London's £10 billion transport investment programme.

However, the Conservatives said there were fewer shoppers in central London, with small businesses among those losing out as a result.

"We also now know that congestion levels are stagnant at the moment, making this increase purely about filling Mr Livingstone's coffers," added Bray.

"Having said in the past that the charge would not be increased for at least a decade – this is also yet another example of Mr Livingstone breaking promises.

"Its time he scrapped this proposed rise – once and for all."