The Commons Treasury Select Committee has broadened its inquiry into the controversial private equity industry.

It has called CVC Capital Partners, which led the 2004 acquisition of the AA, to give evidence next week. Alchemy Partners, whose founder Jon Moulton is one of the few vocal members of the secretive industry, will also appear at the scheduled hearing next Tuesday, which also includes Blackstone and Duke Street Capital.

The news that the MPs are stepping up their investigations comes as the GMB has written to the committee demanding that Permira, CVC and Charterhouse be called to submit evidence after the £6.2 billion merger of Saga and the AA. The union is furious that £4.8 billion of fresh debt has been piled on to the merged company while the three private-equity owners took £2 billion in profits.

The deal was announced a week after four leading private-equity practitioners, including Damon Buffini, of Permira, faced questioning from the committee as part of its inquiry into the industry’s disclosure, transparency and tax breaks.

In a letter to John McFall, the Labour chairman of the committee, Paul Kenny, the GMB general secretary said: “It is apparent to us that Mr Buffini must have been aware of this very lucrative merger deal when he gave his evidence and that the deal itself provides a very instructive opportunity to evaluate the negative impact of the private equity industry.”

This week Saga, the insurance and travel firm for the over-50s, and the AA car breakdown service agreed to merge in a deal involving Andrew Goodsell, Saga’s chief executive, receiving £144 million and Tim Parker, head of the AA, receiving about £40 million.

Last week’s committee lineup included Mr Buffini, senior partner in Permira, but did not include Rob Lucas from CVC, who brokered the original AA deal and who proposed the Saga merger. Nor did it include any representatives from Charterhouse, the secretive private equity firm that owned Saga.

Sources had told The Times previously that the committee was considering expanding its inquiry to include other high-profile buyout firms.

Michael Fallon, a Conservative MP on the committee, said: “It is extremely unlikely we would look at any particular deal. That’s not the purpose of the inquiry.”

The AA has become the whipping boy of unions campaigning against the buyout industry. They say the deal epitomises the firms’ role as “asset-strippers”, buying companies on the cheap, cutting thousands of jobs and making off with all the profit. In the AA’s case, CVC and Permira cut 3,000 jobs after buying the breakdown service for £1.7 billion in 2004.

It also emerged yesterday that Gordon Brown, the prime minister to be, has appointed Mr Buffini to a new “Business Council for Britain” in a move likely to infuriate the unions.

Times Recommends

• Lies and cover-up at MG Rover exposed by report
• High oil prices push manufacturing costs up
• Primark founder steps down as chief executive