Mr Milburn said professions needed a wider pool of talent
Former cabinet minister Alan Milburn is to return to the political front line in a key advisory role to Gordon Brown.
The ex-health secretary is to head a new commission on social mobility.
Mr Milburn, who is seen as a Blairite, will chair a panel of industry leaders to help people from disadvantaged backgrounds get on in key professions.
He told the BBC it was vital children from all classes got a "fair crack of the whip" when it came to developing their careers.
Measures to promote social mobility are to be set out in a white paper on Tuesday.
Ministers have identified limited access to the professions - such as law, medicine, the senior civil service, media, finance and the upper ranks of the Armed Forces - as a major obstacle.
Mr Milburn, MP for Darlington, will chair a panel of representatives from the professions who will generate proposals for what they can do to widen access in their sphere.
Issues to be considered include financial obstacles to access and progression, the role of work experience and internships, recruitment practices and what can be done to encourage new applicants for certain jobs.
Mr Milburn told BBC Radio 4's The World This Weekend: "The government and Gordon Brown are absolutely right to do everything possible to get Britain through the economic downturn.
"And there's a broader set of issues for the long term."
He added: "It's important for the future of the professions themselves that they are fishing in the pool of the widest possible talent."
In a Sunday Times article he wrote: "With 90% fewer unskilled jobs and 50% more professional jobs expected in Britain by 2020, our future success depends on unlocking the talents of all our people."
The new Panel on Access to the Professions will include Michael Grade, executive chairman of ITV; Gail Rebuck, chairman and chief executive of publisher Random House; Azeem Ibrahim, founder of the European Commerce and Mercantile Bank; and Trevor Philips, head of the Commission for Equalities and Human Rights.