JEREMY CORBYN’S successful leadership campaign launched a new group of the left yesterday to transform Labour into a “mass movement.”

Momentum will be independent of the party leadership but was welcomed by Mr Corbyn as offering to “put the people’s values back into politics.”

It will hold mass rallies and seek to organise activists inspired by Mr Corbyn both inside and outside the Labour Party.

The announcement returned Mr Corbyn to the front foot after his critics whipped up a new controversy over whether he would attend a meeting of the Queen’s secretive Privy Council, of which the Cabinet is merely a standing committee.

The Labour leader was accused of “snubbing” the Queen — but it emerged he was being appointed to Britain’s top governing body by written order due to a private engagement.

Momentum’s launch follows years of discussions about bringing together activists from different groups on the Labour left.

Existing organisations including the Campaign for Labour Party Democracy and Red Labour are known to have been involved in pre-launch discussions.

But activists hope that Momentum will become an outward-looking mass organisation rather than the sum of several internal pressure groups.

It will not initially be a membership organisation and has been incorporated as a director-led company until democratic structures can be established.

“Now more than ever we need to unite and continue to build our movement to change our politics and to win together in 2020,” said Mr Corbyn.

“To do this, we need to keep up the momentum we have built over the last four months.”

Momentum will be seen as a challenge to Blairite lobby group Progress, itself formed after Tony Blair’s successful 1994 leadership campaign.

Though it has always had limited support in the grassroots, Progress’s formidable organising machine has resulted in its supporters ­dominating parliamentary selections and Labour’s ideological debate.

Labour MP Clive Lewis, who is set to play a key role, said that Momentum would turn Labour “into a democratic institution worthy of its founders’ original aspirations.”

In an article for the New Statesman he wrote: “The array of vested interests confronting us cannot be taken on by one man or even a single political party in Westminster. Instead, we need a bigger, broader, deeper alliance.”