Medical schools should widen the pool of talent from which doctors are recruited by making it easier for youngsters from poorer backgrounds to study medicine, a report has urged.
Labour's former health secretary Alan Milburn, the government's independent reviewer on social mobility, accused medicine and other professions of failing to make "any great galvanising effort" to open their doors to disadvantaged students.
His update on progress since an earlier report in 2009 will say that there should be more effort to give teenagers from state schools work experience in the professions, including one-year foundation courses at medical schools.
But representatives of the professions insisted they were already taking action to open up their ranks to a broader range of candidates.
Louis Armstrong, chairman of the organisation Professions for Good, said: "Professions are now much more aware of the need for, and value of, diversifying both their membership and their routes of entry.
"Many professions now have a range of ways to join and qualify, including non-graduate routes."
Milburn's report is expected to say that 83% of jobs created in the next decade will be in the professions, increasing the proportion of the working population in professional careers from 42% to 46% by 2020.
This ought to provide an opportunity for increased movement between the classes of the kind seen in the 1950s, as long as the doors to jobs are kept open for people from all backgrounds, the report is expected to say.
But Milburn told the Guardian: "We won't get a more mobile society unless we create more of a level playing field of opportunity.
"With medicine and with too many other professions, I see no great galvanising effort to change.
"It is deeply regrettable since medicine has made such great progress in diversifying its intake in terms of race and gender. The medical profession knows what it needs to do, but frankly it is not doing it.
"I wouldn't view it as positive discrimination. I view it as widening the pool of talent from which medicine recruits."
Armstrong said that the professions had already done a lot to address obstacles to social mobility raised by Milburn in his earlier report, citing a 2011 code of practice for internships and a social mobility toolkit published earlier this year.
But he added: "There is undoubtedly much more to be done: promoting more widely those diverse entry paths; working with schools and the new National Careers Service to provide much better advice and guidance than has often been available to disadvantaged children and young adults; helping to raise aspirations and demystify the professions; broadening our mentoring activities; encouraging employers to diversify their recruitment policies.
"The list is long and there is no magic bullet. All professions are now at work on this important agenda. We are determined to play a full part in the Government's long-term social mobility strategy."
The chief executive of the Institute of Chartered Accountants in England and Wales (ICAEW), Michael Izza, said: "Professions like accountancy have always been major drivers of social mobility in society.
"We are once again leading the way by opening up new routes into a professional career, through apprenticeships, pioneering projects in disadvantaged communities, but also by encouraging our member firms to offer a more diverse range of graduate internship opportunities."
Milburn told the BBC Radio 4 Today programme: "There are two great opportunities. Oddly enough, the global financial crisis and economic downturn has increased social concern about inequality and unfairness, so there is a political pressure.
"Secondly, there is an economic pressure. We know from the history of our country the chances of social mobility are greater if there are more professional jobs available... there is potential for another big social mobility drive today because the British economy is changing, it is becoming more professional.
"There is potential here, providing there is opportunity for all of those with ability and aptitude and aspiration to get on the career ladder... I'm afraid when it comes to that there is a long way to go."
Milburn said there were questions over barriers put up by professions, such as access to work experience, and it was a job for careers services, universities and employers as well as government.
And he added: "Education is the big motor for social mobility, we know that."
Deputy Prime Minister Nick Clegg said Milburn accused some of the professions of "shutting out opportunity".
He told Sky News it was important to have an independent reviewer so that "our feet are held to the fire to make sure that we make the changes necessary to boost social mobility over time".
He said: "You can't turn around something as complex as the lack of social mobility in Britain overnight. Even when there was lots of money sloshing around the system, social mobility still didn't improve, so it's obviously a complex issue which you need to deal with through good times and bad, thick and thin."
The Liberal Democrat leader said Milburn had "trenchant criticisms to make" about professions including medicine, journalism, law and politics, claiming that "too many of those professions are still, in effect, shutting out opportunity for youngsters who are under-represented in those professions".
Barnardo's chief executive Anne Marie Carrie said: "It is absolutely right that we support disadvantaged and vulnerable young people with potential to enter the professions.
"But we must not forget that there are many whose life chances will be most profoundly improved by ensuring that they have the basics in literacy and numeracy.
"Only by getting the basics right and by giving marginalised young people the right opportunities, will we enable them to climb out of poverty and onto the first rung of the employment ladder."