Image caption Lord Wei is a former management consultant

The man in charge of implementing David Cameron's Big Society plan has announced he is standing down.

Lord Wei said it had been "an honour" to be part of the project and he would now be taking on a role at a community action charity.

The prime minister said the peer had played an important role in initiatives like the Big Society Bank.

Mr Cameron has called the Big Society his "mission in politics", but Labour says it is a cover for spending cuts.

The Big Society was the Conservatives' flagship policy at the last general election and is based around a desire to shrink the role of government and devolve power to local communities to run their own services.

The Cabinet Office said Lord Wei "remained a committed advocate" of the idea and would "continue to champion the cause of social action in the House of Lords".

Earlier this week, the prime minister gave a speech about charitable donations and volunteering to promote the Big Society - but Labour called it "the latest in a long line of desperate attempts to rescue [the policy]".

'Modest role'

Lord Wei of Shoreditch, who sits on the Tory benches, was a member of Teach First's founding staff team, a charity which trains high-flying graduates for careers in tough inner-city schools.

The former management consultant was appointed as a government adviser in 2010 and was later ennobled.

Analysis When Lord Wei became a government adviser last year, he seemed to personify the very idea of the Big Society. This 30-something wunderkind had given up a lucrative career in management consultancy to become a "social entrepreneur", working for innovative charities. His loss from the heart of government may not mean a downgrading of the Big Society - David Cameron this week emphasised that the policy wasn't "some fluffy add-on to more gritty and more important subjects" - but as he departs, Downing Street has lost someone of strong symbolic significance. The opposition have already accused Mr Cameron of having to re-launch the Big Society four times, and even on the Conservative benches, there are those who have always felt the idea is "too woolly", lacking in clarity and inspiration. Lord Wei himself said the Big Society required a culture change that could take two parliaments to achieve, but critics will doubtless wonder aloud whether the idea will last much longer than its proponent.

He is standing down from his unpaid post to work for the Community Foundation Network.

"I look forward to taking on this new role where I will be getting out into communities and advising investors, organisations and community leaders in helping them to transfer power and resources from the centre to where it is really needed," he said in a statement.

"I will always be proud to have played a modest role in helping lay the foundations here on which the Big Society will be built in years to come. I want to thank everyone, but particularly the prime minister, for giving me this opportunity and for pursuing this vision with courage and determination.

"I look forward to helping in my own small way outside government - because it is out there, in local communities, that the heavy lifting must now be done."

Mr Cameron said Lord Wei had worked "incredibly hard" to help develop policies that support the Big Society.

"He has played an important role in delivering key initiatives like Community Organisers, National Citizen Service and the Big Society Bank," the PM said.

"I wish him every success in his new role."

For Labour, shadow Cabinet Office minister Tessa Jowell MP said "yet again" the Big Society was "descending into farce".

"Only a day after Cameron told us all to take more responsibility, it appears that there will now be nobody in his government responsible for bringing the Big Society into reality," she added.

In his maiden House of Lords speech, Lord Wei described the Big Society as "a coral reef" and the policies around it as "nurturing an ecosystem".

He said public services were "the seabed", the various providers of those services were the "coral", and the local citizen groups involved in running them were "the fishes".

In February, it was announced that Lord Wei would be resuming his "agreed hours", having worked overtime since his appointment.

He was reported as saying he wanted to cut back his government work so he could earn money and have "more of a life", but that was denied by the Cabinet Office.