John Prescott will chair nine Cabinet committees and deputise for Tony Blair on seven others, it has been announced.
Mr Prescott: Lost department in reshuffle
The prime minister's office outlined his roles as Mr Prescott answered questions from MPs for the first time since being stripped of his department.
The deputy prime minister had a rough ride in the Commons, with much ribald humour about his affair.
The Tories have attacked Mr Prescott for keeping his salary and perks despite "seemingly doing very little".
In response to questioning about his role, Mr Prescott said: "I am doing far more than [former Deputy Prime Minister] Lord Heseltine did.
"No complaints were made about Lord Heseltine at the time. I am doing far more work than he did, I am fully justifying the work I am doing."
The prime minister had given him an important job to do which he was now getting on with, he said.
"I think the prime minister felt I was able to play a role, a more central role, in government than I could have done when I had a huge department to run and was deeply involved in the day-to-day activities of a department," he added.
"If I was to play a more central role then I think it was understandable that I would be removed from frontline administration of one of Whitehall's largest departments, and that is what happened."
He added: "That is not my description of the role of the deputy Prime Minister. It is the description of Lord Heseltine ... in 1996."
Conservative frontbencher Oliver Heald said Mr Prescott's main role was as a "marriage guidance counsellor" between Tony Blair and Chancellor Gordon Brown before arguing the Labour Party and not the taxpayer should pick up his salary.
In his statement Mr Blair said his deputy would have a "wide-ranging brief across a range of domestic policy areas".
DPM's Cabinet committees
Housing and planning
Local and regional government
Animal rights activists
Post Office network
Mr Blair also confirmed that his deputy would continue to use his grace and favour country mansion at Dorneywood.
Mr Prescott has already stressed his continuing role in brokering deals on thorny policy issues. He said Mr Blair asked him to "negotiate solutions" to difficult policy areas.
Of the nine committees only five are full Cabinet committees. The other four being Cabinet sub-committees.
Mr Blair said "The deputy prime minister will be supported by a private office and secretariat, allocated from within existing civil service resources.
"In his Cabinet committee work, he will be supported by the Cabinet Office's secretariats, and will draw on the support of officials in other departments as necessary to fulfil his other responsibilities."
Local government strategy
Mr Prescott will also deputise for Mr Blair on seven further committees: anti-social behaviour, asylum and migration, energy and the environment, NHS reform, public service reform, schools policy and serious organised crime and drugs.
The prime minister said the main way of agreeing policy across departments was through Cabinet committees and sub-committees.
Mr Prescott has insisted he talked to the prime minister about dropping his department before the furore over his affair with his diary secretary, Tracey Temple.
Theresa May, for the Conservatives, said there were real questions over Mr Prescott's role and the fact that he had kept his £134,000 salary, particularly if his job was merely acting as a broker between Mr Blair and Chancellor Gordon Brown, as has been suggested.