Labour's former work and pensions secretary John Hutton has been unveiled as the chair of an independent commission on public service pensions.
The appointment sparked outrage in some quarters, with John Prescott calling his former government colleague a "collaborator".
Lord Hutton, who was ennobled in the dissolution honours, was one of five Labour ministers who left the Cabinet during Gordon Brown's leadership crisis in June 2009.
He welcomed the opportunity to lead a "root and branch examination" of reform of public sector pensions after being asked to do so by Conservative chancellor George Osborne.
"The long-term sustainability and affordability of public sector pensions is crucial for sustainable public finances both in the UK and internationally," Mr Osborne said.
"John is an experienced public servant, who I know will bring a clear and unbiased analysis to bear on this complex and important issue."
But Lord Prescott - ennobled at the same time - attacked the move.
"I've been in politics for over 50 years but even I can't believe what's happening," he wrote on his blog.
"They've made themselves human shields for the most savage and heartless Tory policies in 20 years."
Lord Hutton's commission has been tasked with assessing the growing gap between public and private sector pensions provision, the need for fairness across the workforce and how risk should be shared between the taxpayer and the employee.
There are no plans to undermine existing accrued pension rights, but the commission is expected to recommend how pensions can be made "sustainable and affordable in the long-term".
Lord Hutton, who stood down as Labour's MP for Barrow-in-Furness at the general election, said: "Reform of public sector pensions is a huge challenge for both the public finances and the public sector workforce.
"I am determined that this work should be conducted openly and transparently and that our conclusions will be underpinned with a comprehensive analysis and evidence-base."
The commission will publish its final report in time for the 2011 Budget.