The Mayor said the lobby was a "waste of time"

Joined by Rail Maritime and Transport union officials they campaigned at the Mayor's State of London debate at the QEII Centre in Westminster on Saturday.

RMT union general secretary Bob Crow said some cleaners were paid "rock bottom" rates.

But the Mayor said he has always said they should receive the living wage.

'Pay scandal'

He added that it was therefore a "waste of time" picketing the State of London debate.

'I have repeatedly made clear that I believe that the living wage should be paid to all staff by the private companies that now manage London Underground's infrastructure and cleaning under the Public Private Partnership (PPP) imposed upon us by the government," said the Mayor of London Ken Livingstone.

He said he has always made it clear that he supports the trade unions' campaign for the PPP companies to pay all of their staff the living wage.

"It is therefore a waste of time to picket the State of London Debate when the trade unions should be directing their protests at the PPP companies who set their members' pay and conditions completely independently of myself and Transport for London," he said.

Key issues

But Bob Crow said earlier: "The Mayor has called this conference to discuss how everyone can benefit from London's success.

"A good start would be to end the scandal of poverty pay and ensure that the people cleaning London's stations and trains get paid at least the London minimum wage of �7.20 and get at least 28 days' paid holiday."

The State of London debate is an annual event which brings Londoners together to discuss key issues affecting them.

It is being held from 1000 BST to 1645 BST.