By Nick Assinder BBC News Online political correspondent

In politics, just like comedy, timing is everything.

So the latest report on government advisors by the Commons transport committee could not have come at a more appropriate time.

But it is not designed to put a smile on Tony Blair's face.

Just as the Jo Moore affair refused to die down, with the suspension of Ian Jones, and Sir Nigel Wicks announcing a new inquiry into spin doctors, the committee delivered one of the most biting attacks yet on the government's reliance on advisers.

Dunwoody summed up concerns

The Labour-dominated group, headed by the formidable backbencher Gwyneth Dunwoody, effectively confirmed all the worst fears about Tony Blair's administration.

In the most telling phrase - and one that is certain to haunt the government for years to come - the committee declared: "Never in peace time has a prime minister gathered about himself such an assemblage of apparatchiks unaccountable to Parliament. In effect, a prime minister's department has been created."

No surprise

Most regular observers of Downing Street will be less than knocked over by surprise at this finding.

But the strength of the language in the unanimous report is unprecedented.

The committee's inquiry may have started out as a probe into the refusal to appear before it of Tony Blair's new transport adviser Lord Birt.

But it instantly and inevitably turned into an investigation into advisers and No 10 Downing Street itself.

Moore affair rumbles on

And, according to the committee, the "prime minister's department" not only obstructs select committee work but is undermining cabinet government itself.

The report just about sums up all the concerns of those opposed to this uniquely New Labour approach to government.

In one way or another, the activities of these unelected and unaccountable apparatchiks now touches the daily routine of everyone involved with the government or Whitehall.

Fresh curbs

Advisers have existed under all governments, but no one would deny they now occupy a far more powerful place in government than at any time in the past.

And every report into their activities has called for fresh curbs.

The government now says it is ready to introduce legislation which might address some of these issues and, specifically, the relationship between advisers and civil servants.

And the demands for the role of these advisers to be clarified and limited are clearly now coming to a head.

Many are hoping the recent controversies will finally mark the beginning of the end of the spin doctors' power.

Others, however, believe the government's declarations are themselves spin and nothing is about to change.