London Underground is continuing to withhold vital PPP documents from Transport for London

Bob Kiley, London's transport commissioner

Both men have led the opposition to the PPP plan, but last month Transport Secretary Stephen Byers announced that the Government was pressing ahead with the �16bn plan.

London Underground (LU) recently wrote to Mr Livingstone requesting more time to produce a "considered" response to the PPP proposals.

However, on Saturday Mr Kiley said the extension until Wednesday would be unacceptable.

"LU is continuing to withhold vital PPP documents from Transport for London (TfL)," he said.

"LU's offer to respond to TfL's request for missing PPP documents and private sector profits on Wednesday - two days before the end of the unilaterally imposed consultation period - is totally unacceptable."

Although Mr Kiley said legal action would be started if the documents had not been received by Monday, it later emerged the original request from LU had been granted.

The original deadline was announced after a "strongly worded letter" sent to Sir Malcolm Bates, London Regional Transport's chairman, went unheeded, according to Mr Livingstone.

The mayor also wrote to Transport Secretary Stephen Byers outlining the situation.

Mr Byers wrote back to Mr Livingstone asking him not to start legal action.