In a series of appointments to his political office, Mr Hague rewarded Mr Duncan by making him his Parliamentary Political Secretary.
It is an unpaid appointment, but like Mr Mandelson's post in the Labour Party, it carries untold influence.
Mr Duncan will be in charge of trying to ensure that the party and the 164 Tory MPs stick to the agreed line on policy, raising fears among pro- European Tory MPs that it will mean enforcing opposition to the single European currency.
Mr Duncan said that he would be "helping to ensure that the Conservative Party speaks with one voice".
Like Tony Blair's minister without portfolio, Mr Duncan is regarded as a Machiavellian figure behind the leader of his party, who has made enemies for his razor-like ability with the parliamentary put-down. He is also rated highly for his spin doctoring skills and was the driving force behind the slick and skilful presentation of Mr Hague as a "fresh start".
Acting as the go-between for the Conservative leader and his party chairman, Lord Parkinson, Mr Duncan, will play a crucial role in the shaping of the image of the new Tory party under Mr Hague, and the sharpening of its attack on Labour.
Mr Hague also announced four other paid appointments to his private office, including two MPs who lost their seats at the election: Charles Hendry, the former Tory MP for High Peak, chief-of-staff; Sebastian Coe, former Tory MP for Falmouth and Camborne, as his deputy chief-of-staff; George Osborne, former political adviser to Douglas Hogg, as his political secretary; and Mark Fox, a former Central Office researcher as political office assistant.
Meanwhile, new dissent broke out in the Conservative Party as the foundation that ran John Redwood's campaign office launched a full-frontal attack on the leadership.
The row over the future of the Conservative 2000 think-tank blew up after weekend newspaper reports suggested that it would be closed down now that Mr Redwood had been offered a Shadow Cabinet post.
Yesterday the director of the think-tank, Hywell Williams, accused Conservative Central Office of briefing against Mr Redwood through fear that he would build up an alternative power-base in his old office.
A Sunday Express headline on a story about the foundation's demise claimed: "Hague gets tough in warning to plotters."
Mr Williams said that as director of the organisation he intended to keep Conservative 2000 open.
"One of the things that divided the Tory party during the last period in government was the way in which the centre briefed against members of its own Cabinet. This must not happen again, but what happens first of all is this," he said.
Mr Redwood refused to be drawn into the row, though. He said he had removed his personal belongings from the foundation's Westminster office yesterday afternoon.
"They gave me a lot of support, but I am not offering to do anything for them at the moment," he said.Reuse content