Labour leadership: Jeremy Corbyn urges probe into excluded voters
Labour leader Jeremy Corbyn fears some of his supporters may have been "unfairly" barred from voting in the party's leadership election.
He has handed a list of names to party officials, saying he wants a "fair and open" contest, with all those eligible to take part able to do so.
Allies of Mr Corbyn have claimed there is a "rigged purge" of his supporters after a union leader was excluded.
Labour said it had a "robust" validation process in place.
The Labour Party has, meanwhile, announced it has signed up a security firm to cover its annual conference in Liverpool next month, ending fears the event would have to be cancelled.
The row over voting rights comes after Bakers' union leader Ronnie Draper was barred from voting in the leadership election or attending future meetings, including next month's party conference.
Mr Draper - who represents 20,000 members of the Bakers, Food and Allied Workers Union and who is backing Mr Corbyn in his fight for re-election against Owen Smith - claims his suspension was politically motivated.
He said all he had been told about the disciplinary action against him was it was related to an "unidentified tweet" he posted.
"I have not been given the opportunity to refute any allegations, or a date for any hearing," he said.
"I believe this flies in the face of natural justice. I intend to challenge my suspension robustly and am currently taking legal advice."
The most senior official in the Labour Party, general secretary Iain McNicol, has insisted the decision to suspend Mr Draper had been taken by elected members of the party's ruling body, the NEC, not by unelected party officials as claimed by Corbyn supporters.
But Mr Corbyn has urged the NEC, of which he is a member, to reconsider the move.
"I am very concerned that some people seem to have been unfairly removed from the ability to vote in this election," he said during a trip to Edinburgh.
"A number of people have contacted me as a result of that and we have sent in the names that we are concerned about to the general secretary and asked him to ensure the party checks into this carefully to make sure everyone who is eligible to vote is able to vote in this election.
"We want a fair and open election."
Labour says a "robust validation process" of the almost 650,000 people eligible to vote in the contest will continue until polls close on 21 September.
This includes "verifying all voters share the aims and values of the Labour Party".
In a statement the party said: "The Labour Party has a robust validation process for all votes to ensure every vote cast is eligible in keeping with the Labour Party rules.
"Decisions about individual members are taken by the NEC."
But shadow chancellor John McDonnell, a staunch ally of Mr Corbyn's, said Mr Draper's suspension appeared to be "part of a clear pattern of double standards" and must be properly justified.
He asked why action had not been taken against Labour peer Lord Sainsbury, who gave the Lib Dems more than £2m during the EU referendum campaign, or donor Michael Foster over an article referring to "Jeremy Corbyn and his Nazi storm troopers".
"Both will, as things stand, be able to vote in this election," Mr McDonnell said.
"Meanwhile, thousands of other members and registered supporters are reported to have been denied a vote without being given an explanation or opportunity to challenge the decision or process.
"Labour party members will not accept what appears to be a rigged purge of Jeremy Corbyn supporters. The conduct of this election must be fair and even-handed."