Lord Mandelson: Whitehall's Emperor, or just a team player?

He faced a barrage of questions from MPs given a rare chance to discover more about his job

He has accumulated a 36-word title, a coterie of 10 loyal ministers at his beck and call, and a department that has ballooned into one of the biggest ever seen in Whitehall. But Lord Mandelson has defended the formidable empire he has built since playing a key role in preventing the toppling of his former political rival, Gordon Brown.

After being handed a swathe of new responsibilities at last month's reshuffle, the newly installed First Secretary of State was confronted yesterday over how he found the time to do justice to his vast array of responsibilities as well as clinging to the notorious influence he now wields over the man who brought him back to the front line of British politics.

Appearing before the Commons Business Committee, Lord Mandelson denied claims that the department had been set up solely around "one man's ambitions", explaining that his newly formed Department for Business, Innovation and Skills was charting the country's route out of recession and ensuring Britain's industry could compete in the future.

"Any future government should see the sense of bringing these responsibilities and areas of policies together under one roof," he said. "The aim of the department is very simple – to help the UK to excel and thrive in the future world economy."

Lord Mandelson's new-look section has seen an entire Whitehall department swallowed up into his territory. The decision to place the former Department for Innovation, Universities and Skills under Lord Mandelson's control was a genuine surprise to many ministers during Mr Brown's emergency reshuffle last month.

Many suspect that the department will not survive beyond Lord Mandelson's tenure at its helm, believing it was invented to give him the gravitas that properly reflected the central role he now has in directing government policy.

Lord Mandelson was challenged yesterday about his sway in Downing Street, with Peter Luff, the chairman of the committee, asking him whether he was "this Prime Minister's Willie?"

Judging by the guffaws that rang out, the reference to Margaret Thatcher's deputy, Willie Whitelaw, and her famous comment that "every prime minister needs a Willie", was not lost on the committee. Nor did it fall short for the Business Secretary, who replied: "I am tempted to extend that metaphor, but decorum..."

He also said the position of deputy was not unusual. "I am not the first to be playing the role," he said, arguing that the same work had been done by Rab Butler and Harold Macmillan in days gone by for the Tories.

But it is no secret that it was Lord Mandelson who played a key role in persuading ministers to hold firm behind Mr Brown when he looked likely to be toppled as Labour's leader. He has been amply rewarded.

After his new appointment, the shadow Business Secretary, Ken Clarke, was quick to point out to the new First Secretary of State that his remit now stretched from "space to defence sales to universities and further education".

While he admitted yesterday to spending a fifth of his time "supporting the Prime Minister and Government" with duties, many suspect Lord Mandelson's opinion is sought on a far more regular basis. Mr Brown's long working days will often see his right-hand man summoned by telephone at first light. The shadow Foreign Secretary, William Hague, has accused him of becoming the most powerful unelected figure since Cardinal Wolsey's power of the mind of Henry VIII. It has led to fears that crucial areas of the Government's work could be sidelined as a result of Lord Mandelson's role in keeping Mr Brown's leadership afloat.

The lack of accountability of Lord Mandelson's department was also raised yesterday, with five Lords now among his 10 ministers. His acolytes also give him a hefty presence around the Cabinet table, with three of his team able to attend the meetings when their topics are due to be discussed.

He is also plugged into Mr Brown in more ways than one. Though he spends more time than he would like to admit with the Prime Minister, dealing with the daily traumas of life at No 10, ministers such as Baroness Vadera and Lord Davies, both under his charge, also have the Prime Minister's ear.

For Lord Mandelson, a man seemingly running out of time in power as Labour look set for election defeat, his elevation to the de facto deputy leader has allowed him to fulfil at least part of his ambitions to emulate the achievements of his grandfather, Herbert Morrison. It appears that his ultimate goal of matching his grandfather's rise to Foreign Secretary will end in frustration, as the Prime Minister simply could not do without him close at hand.

But the labours of the Rt Hon Lord Mandelson of Foy in the County of Herefordshire and Hartlepool in the County of Durham, First Secretary of State, Secretary of Business, Innovation and Skills and Lord President of the Council, are far from over.

Indeed, his most difficult job is yet to come. Talk has already begun on the Labour benches of a further attempt to oust Mr Brown in the autumn, around the time of the Labour Party conference. If the expected assault materialises, it will again be up to Lord Mandelson to lead the defensive blitz, and ensure that the man he once plotted against is still in his place to fight an election.