More than 100 Green Party candidates have tried to join Labour in the latest evidence of entryism by people who want to vote for Jeremy Corbyn in the party’s leadership contest.

A trawl of Green candidates in this May’s general and local elections by Labour officials found that about 4 per cent of them have applied to join Labour since then. Between 100 and 150 Greens have had their applications rejected.

Labour had already uncovered evidence of infiltration by members of hard left groups who oppose the party, such as the Trade Union and Socialist Coalition. Some Labour MPs believe the party may decide next week to delay or suspend the contest to give it time to weed out people who do not support the party.

One MP said: “There is panic at Labour headquarters as more evidence emerges.” However, a Labour spokesman insisted last night: “We do not have plans to suspend or delay the contest.”

Green Party members and supporters - including its leader, Natalie Bennett - on the campaign trail in Manchester earlier this year (Getty) (Getty Images)

He added: “We are identifying everybody who stood against the Labour Party in the last couple of years and checking that against those who want to take part in the leadership contest. Once identified, they will not get a vote.”

Labour has confirmed that 65,000 of its 275,000 full members joined since the general election. Another 35,000 have paid £3 to become registered supporters, which gives them a leadership vote. A further 35,000 trade union members have signed up as affiliated supporters. It is understood another 20,000 members have joined since these figures were released – including 7,000 over the weekend before last.

Any decision to delay the vote would have to be approved by Harriet Harman, the party’s acting leader, and its National Executive Committee. The last date for recruits to sign up and be eligible to vote is 12 August. Ballot papers are due to go out on 14 August. The ballot closes on 10 September, with the result announced two days later.

Supporters of Andy Burnham, Yvette Cooper and Liz Kendall suspect that many new recruits will back Mr Corbyn. Any intervention would be controversial, and bound to be seen by left-wingers as a desperate attempt to prevent a Corbyn victory. Mr Corbyn dismissed claims of an entryist plot as “absolute nonsense”. He told the London Evening Standard: “What’s fascinating about this process is the number of young and old people who are coming out together to talk about how we can have something different from austerity.”

Some Conservatives have tried to sign up as supporters to vote for Mr Corbyn. Tim Loughton, the former children’s minister, was caught and blocked. He said he had no intention of voting, but wanted to “blow the gaff on... a complete farce”.

The Green Party said it “has made no attempt to influence the Labour leadership contest in any way and has no intention to do so. We respect the democratic decision-making processes of other political parties.”