Powell refused to talk to committee

And, for the second time in as many days, a Commons watchdog has rebuked the government for refusing to cooperate with their inquiries.

On Monday it was beleaguered Europe minister Keith Vaz who was attacked for refusing to help the standards watchdog probing his affairs.

Shadowy work

Now it is the prime minister himself and his aide Jonathan Powell who have been rebuked for refusing to appear before the Labour-dominated public administration committee during its investigation into the role of special advisers.

That all adds to the impression that Tony Blair is not only happy to see advisers continuing their shadowy work but does not want the spotlight thrown onto their activities.

Probably the most high profile adviser is Mr Blair's own official spokesman, Alastair Campbell.

He has been routinely accused of wielding far too much power in Whitehall and is widely branded as the real deputy prime minister.

It was Mr Campbell who shot off withering memos to ministers a couple of years ago, ordering them in effect to do as they were told.

And it was Mr Campbell who is said to have played a major role in persuading the prime minister to dump former Northern Ireland secretary Peter Mandelson over the Hinduja affair.

Chancellor Gordon Brown's former adviser Charlie Whelan was also notorious for his blunt approach to manipulating the news agenda and promoting his boss.

Rubbishing ministers

Not all advisers behave in this way. They are paid for out of the public purse but, unlike most civil servants, are expected to offer both specialist and political advice to their ministers.

But increasingly the likes of Mr Campbell, Mr Whelan and others have become full-blown spin doctors.

They not only offer advice to their bosses but take high-profile roles with the media, pushing the government line and rubbishing the opposition - and quite often other ministers.

They have become hugely important in the political process and journalists who fail to toe the line often find themselves frozen out of their off-the-record briefings.

But what worries the committee and many others is not that the spin doctors get up to these antics, but that they do it under the cover of the civil service and while their salaries are being paid by the taxpayer.

There are growing demands for them to be funded by the political parties themselves and, as the new report shows, pressure for some curbs on their activities is not about to subside.

William Hague has pledge to slash the number of advisers in Whitehall if he comes to power.

But the question most want answered is whether New Labour - which is widely seen as the creation of the most famous spin doctor ever, Peter Mandelson - can ever kick the habit.