Tory leader David Cameron launched a charm offensive on Britain's ageing population yesterday, claiming they had been "airbrushed" out of society.

The opposition leader said Labour had been focusing on young people for too long and should look to the over 50s to provide a crucial contribution to the economy.

In a speech to organisations, including Age Concern, Mr Cameron said retirement should be a "process, not an event" allowing people to reduce their hours and responsibilities gradually.

But, during the event at the Design Museum in east London, he refused to support a total ban on company retirement policies.

He insisted it would make business less inclined to hire older people.

Neil Churchill, from Age Concern, described Mr Cameron's words on company retirement policies as a "bit of a fudge".

He said employees should not be forced out of a job because of their age.

But, Mr Churchill said he was pleased a senior politician was taking the issue of an ageing population seriously.

He said: "There is a vacuum in British politics as nobody has recognised the Baby Boom generation, born after the Second World War.

"David Cameron has acknowledged that and started to show that he understands the kind of pressures that Baby Boomers are under.

"He understands the fact that older people are very significant contributors to society."

Mr Cameron said older people were too easily stereo-typed as needy and taking from society.

"For many years older people have been airbrushed out of the picture. They don't feature too much on TV. They are seen as somehow outside popular culture and they don't get a lot of attention in politics."

But he claimed that the million people over 50 who want to work and could work, could contribute up to £30 billion to the economy.

"Rather than seeing older people as liabilities, we need to see them as contributors," he said.

"That doesn't mean they are going to work flat out like they did when they were 30. But the important thing is that they should be able to work part-time after the age of 65 if they want to. We need to see retirement as a process, not an event - a slope, not a cliff.

"We need to allow salaries to coast downwards from their peak, as workers take on lighter responsibilities and shorter hours."

The Lib Dems criticised Mr Cameron's speech, accusing him of lacking credibility.

Nick Clegg, shadow home secretary, said: "Once again, presentation has triumphed over substance. Vague assurances that the Conservatives want to befriend voters over 55 will not wash. "Vague assurances that the Conservatives want to befriend voters over the age of 55 will not wash."