Labour has called in lawyers to ensure its leadership election is complying with party rules amid fears over the contest being infiltrated by supporters of other parties.
Acting leader Harriet Harman has sought legal advice to ensure that the process is being carried out with integrity and cannot be open to challenge.
The contest has been plagued by concerns over "entryism" from hard left individuals and Tories seeking to influence the outcome of the race to succeed Ed Miliband.
The fears have arisen as the election is operating under new rules introduced by Mr Miliband which allow members of the public to sign up to vote as a "registered supporter" for £3.
Ms Harman's spokeswoman denied that legal advice had been sought as a result of the worries.
She said: "The party's focus is on making sure that the 2014 rules are fully complied with, as we said last week we have taken legal advice to make sure that the rules are being complied with and that all due diligence as possible was being done.
"But there were no plans to halt or suspend the contest.
"We keep a close eye on the process."
Meanwhile, surprise frontrunner Jeremy Corbyn claimed his anti-austerity message could win back support from former Labour voters who have drifted to Ukip.
The left-winger said his call for higher public spending has gained support on the campaign trail in areas where Ukip has performed well.
Speaking after addressing a packed rally of 1,200 supporters in Newcastle, with 1,000 more waiting in the rain outside, Mr Corbyn told the Press Association: "We lost seats due to the lack of any clear economic alternative and I found campaigning in Ukip areas that when I engaged people on the level of jobs, on schools, on housing and on health and on anti-austerity we got support.
"But if all we could offer was cuts, but done in a slightly different way than the Tories had done for the last five years, then people simply didn't want to know."
Bookmaker Paddy Power has already paid out on bets that Mr Corbyn will win the contest while Scottish newspaper the Daily Record has endorsed the Islington North MP.
Mr Corbyn said: "I'm obviously pleased to have the backing of a paper that has such a long tradition of support for the Labour Party.
"I'm sure that at least in part, this endorsement will have been made with Labour's future in Scotland in mind, which is important as Labour has a real need to reconnect with communities in Scotland if we are to succeed across the UK."
But one of his main rivals, Yvette Cooper, remains confident of overhauling the Islington North MP and is set to outline her plan for women's equality.
Ms Cooper's wants to beef up the role of the Equality and Human Rights Commission to look at issues like the gender pay gap and positive discrimination in areas such as executive boards and the judiciary.
Universal childcare for two to four-year-olds, compulsory sex and relationship education, a living wage for carers and protest-free buffer zones around abortion clinics also feature in Ms Cooper's plan.
She will say at a women's event: "David Cameron won't use the f-word. I will. I always have. I'm proud to be feminist. And I want Labour to be championing women's equality again for the future."
Ms Cooper is locked in a bitter battle with Andy Burnham to emerge as the main challenger to Mr Corbyn, while the other contender Liz Kendall lags behind in fourth place.
The result of the election will be announced at a special conference on September 12.