Rebecca Long-Bailey has won the overwhelming support of Momentum activists in the Labour leadership race.

Members of the grassroots campaign organisation that helped propel Jeremy Corbyn to the leadership have also backed Angela Rayner to be the next deputy leader.

Long-Bailey was endorsed by 70% of the group’s supporters, while Rayner won by a much narrower margin of 52%.

But the process drew sharp criticism as activists were asked simply to vote yes or no on whether to support the pair.

They were not given the chance to pick from a list of all the candidates for both positions.

And only 7,395 of group’s 40,000 members decided to take part in the vote.

Laura Parker, who used to run the organisation, said when the process was announced: “Although I am pleased Momentum’s governing body accepted the principle of balloting its members on the leadership, I’m sorry they seem to have decided in advance what the answer is.

“Members should be able to choose from all leader and deputy candidates,” she tweeted.

A Momentum spokesperson said it would now be “mobilising thousands to persuade Labour members” for the leadership campaign.

“Rebecca is at the heart of a new and diverse generation of socialists who recognise that we cannot return to the politics of the past,” the spokesperson said.

“She has spent the last few years pioneering the policies of the future, including a detailed plan for a Green New Deal that can revive communities that have been ignored, bring the country together and lead the world in combating the climate crisis.”

“She is an experienced, principled and inspiring candidate and our movement is proud to support her for leadership.”

Long-Bailey said she was “proud and beyond grateful” to win the endorsement. “I will deliver on the trust Momentum members have placed in me, with a plan to win the next general election and transform our country for the future,” she said.

The latest poll in the race put Long-Bailey as winning the five-candidate battle to become leader, edging shadow Brexit secretary Keir Starmer into second place.

The hopefuls are now in the second stage as they seek to make it to the postal ballot of members and supporters.

They must get the support of 5% of local parties or at least three affiliates, including two unions, representing a 5% share of affiliated members by February 14.