Jeremy Corbyn has said his bid for the Labour leadership has been the "most exciting" period of his life, as reported figures revealed half of those eligible to vote in the leadership contest have signed up since the general election.
According to Sky News, of the 270,000 members of the Labour Party, 70,000 have joined since May 7. A further 70,000 have joined as affiliated supports, largely trade union members, and 50,000 have paid the £3 fee to sign up as a registered supporter.
Labour will not comment officially on the numbers, but if accurate then 190,000 of the 390,000 people eligible to vote have joined since the election.
The surge in the number of people able to vote for party leader has introduced an element of uncertainty to the race - it is not clear who the new members will vote for.
However YouGov's Peter Kellner has said the affiliated trade unionists are helping Corbyn’s chances. "Should he win the overall contest narrowly, these voters will have tipped the balance," he wrote in July.
The veteran leftwinger has emerged as the surprise front-runner in the contest to succeed Ed Miliband and is attracting large crowds at rallies across the country.
The level of support for Corbyn, who was initially seen as the outsider, caught rivals Andy Burnham, Yvette Cooper and Liz Kendall off guard, given he only scraped into the contest.
Speaking in a nature park in Camden at the launch of his environment manifesto today, Corbyn acknowledged his meteoric rise. "Our campaign only started less than six weeks ago when we finally, well, a very excited group of Labour MPs reluctantly put their names to the nomination paper to ensure we were on the ballot paper," he said.
"I thank them for that and I thank those that campaigned to persuade to put their names.We started with absolutely nothing, since then we have developed an enormous campaign all over the country.
"Whatever happens on September 12 we have taken the cork out of the bottle, the candle is burning brightly, the ideas are shining and developing there is a change in the air which is good for all of us.
"It's been the most exciting period of my life ever and an awful lot of people are very excited by the idea that together you can do things, you don't have to sit at home at shout at the television."
Amid fears that Labour is being infiltrated by members of the far-left that want to hurt the party in the leadership election, acting leader Harriet Harman has ordered Labour MPs to check their membership lists.
Some Conservatives have also tried to sign up in order to vote for Corbyn, who they believe will be easier to beat in 2020.
Tory MP Tim Loughton and Tory peer Martin Callanan were both caught by Labour trying to sign up as registered supporters. The party kicked them out but kept the £3 fee.