More than 3,000 infiltrators have been discovered and barred from voting in the Labour leadership contest, a senior party source has told ITV News.
ITV News political correspondent Libby Wiener reports
Contenders Jeremy Corbyn, Andy Burnham, Yvette Cooper and Liz Kendall met with interim leader Harriet Harman this morning to discuss ongoing fears about infiltration by political opponents.
Speaking after the meeting, Ms Harman Labour's interim leader said she was "confident" the integrity of the result - due to be announced on September 12 - would not be called into question.
"I am confident that there won't be questions over the integrity of the result and there aren't any bases for legal challenges," she said.
The four candidates have reportedly all ruled out mounting any legal challenge to the result.
ITV News' Libby Wiener said as many as 3,000 infiltrators had been prevented from voting so far.
Of 3,502 considered by the panel, 3,138 have been ruled ineligible - including 1,972 registered supporters who paid £3 to join the vote.
Some 400 applicants were found to be Tory members or supporters, and 1,900 members or supporters of the Green Party.
Labour later released new figures for the electorate in the leadership race. The total number eligible to vote is now 553,954, including 292,973 full party members - nearly 106,000 more than at the general election. There are 148,182 affiliated supporters and 112,799 registered supporters.
The contest has been plagued by fears that inadequate checks on new members had compromised fairness in the contest.
Mrs Harman stressed that the right of those who were eligible to vote was being protected.
But she warned that people "trying to cheat their way" in would be found and have their vote cancelled.
That process, she said, would carry on "right up until the last minute".