Mr Byers was compared to a messenger

It had asked the Treasury to allow it to question one of its ministers five months ago but the request was rejected.

That prompted committee members to complain that Chancellor Gordon Brown's department was treating them with disdain.

But a spokesman for the Department of Transport said it was Stephen Byers who talked for the government on issues like the Underground.

MPs had argued that the level of influence being wielded by the Treasury meant that PPP was being "imposed" and left Mr Byers in a position where he was "little more than a messenger".

The committee also criticised the decision to plough ahead with PPP despite the fact widespread disquiet of the scheme had been expressed.

Dispute with Number 10

PPP had not been proved to offer better value for money than some of the other options that have been mooted, they said.

The MPs have asked that the House of Commons demand that a Treasury minister appears before them.

The same committee has recently been in dispute with Downing Street after it rejected a request for Tony Blair's transport adviser Lord Birt to give evidence on his role.

A spokeswoman for the department of transport said: "The Secretary of State has given evidence on the PPP on behalf of the government during the committee's inquiry and will discuss the issues further in responding to the committee's report of February 5, and March 7.

Shadow transport spokesman Eric Pickles said the report showed Mr Byers' credibility had sunk to a new low.

"If, as hinted, it is the Treasury, their refusal to be scrutinised by the House of Commons is an act of arrogance beyond belief," he said.

"Londoners cannot expect to receive the best deal for the Tube while ministers concentrate on in-fighting and petty turf wars."