An investigation is to be launched into the new wave of outside advisers, such as the former BBC director general Lord Birt, "parachuted" into Downing Street by Tony Blair.
The all-party Commons Public Administration Select Committee is to investigate the exact nature of the work done by the so-called "blue-sky thinkers" amid growing concern about their role.
Along with Lord Birt, who is working on long-term transport policy, their number includes Adair Turner, a former director general of the Confederation of British Industry, who is conducting a wide-ranging review of the NHS.
MPs on the Labour-dominated committee are worried that the part-time advisers have a powerful role even though it is unclear how they fit into the existing Whitehall structure. They want to know to whom the advisers are accountable and whether they are covered by the code of conduct for special advisers and civil servants.
The committee has already forced the Government to clarify the role of special advisers, political aides funded by the taxpayer, who include Alastair Campbell, Mr Blair's director of communications and strategy. The number of such aides has doubled to 81 since Labour came to power in 1997, including a near-threefold increase at Downing Street to 25.
Now the MPs are to turn their attention to the businessmen recruited to Downing Street's Forward Strategy Unit.
A committee source said last night: "These advisers seem to be extremely influential but their role seems to be very uncertain and hazy."
The MPs are to summon Geoff Mulgan, the unit's head, to answer questions about the work of the outside advisers, which Number 10 refuses to disclose.
After taking evidence from Mr Mulgan, the MPs will consider asking Lord Birt to appear before them. However, such a request might be blocked by Mr Blair on the grounds that the former BBC boss is only a part-time adviser.
The MPs will also question Michael Barber, who leads the Delivery Unit set up by Mr Blair as part of a shake-up that created a Prime Minister's Department in all but name after last June's general election.
The committee, chaired by Tony Wright, Labour MP for Cannock Chase, intends to produce a report later this year that will untangle the complex new power structure at the centre of the Government.
Mr Blair's spokesman insisted the number of people working in the Forward Strategy Unit was "minuscule" but insisted: "It is important to bring in people with different views and different perspectives. Its establishment was part of improving the way government works."
In the Commons yesterday, the Conservative leader, Iain Duncan Smith, taunted Mr Blair about the role of Lord Birt, suggesting that his appointment undermined the Transport Secretary, Stephen Byers. "Who is in charge of transport policy?" Mr Duncan Smith asked.Reuse content