Labour leader urged to 'turn it round pretty quickly' as thousands quit party
Labour members are quitting in protest over J eremy Corbyn's leadership and he must act quickly to stop the exodus, a senior MP has said.
Around 26,000 members have quit since last summer, according to leaked data.
Shadow home secretary Diane Abbott, one of Mr Corbyn's closet allies, insisted the party was still the largest in Europe.
But John Mann said the scale of the membership fall-off was a "concern".
"People who joined to support Jeremy and then have left, it's a pretty quick turnaround," he said.
"We are seeing this trend of people leaving and the longer it continues the bigger problem it becomes.
"We certainly get people leaving because they are not happy with his performance."
Mr Mann said there was always some decline after a leadership election but the figures were higher than would be usual.
He warned Mr Corbyn that he needed to "turn it round pretty quickly".
Mr Mann said: "This is more than the natural drop off you would expect to see.
"It would be simplistic to suggest that this is all to do with Brexit. There are some for that reason but from what I have seen that's not the majority."
Ms Abbott brushed off the membership decline.
She said: "Labour Party loses nearly 26,000 members since mid-2016 report claims. But still biggest political party in Europe."
The apparent shedding of card-carrying supporters led one former chairman of the Parliamentary Labour Party (PLP) to warn the "tide is turning".
More than three-quarters of those to leave the party last year had joined after the 2015 general election, a period that saw membership grow rapidly under Mr Corbyn's leadership.
Figures seen by The Times showed the number of resignations in 2016 was more than the previous six years combined, while more than 15,465 have left since mid-December.
Up to 7,000 members are said to have resigned last month following Mr Corbyn's three-line whip on MPs commanding them to support the triggering of Article 50.
The newspaper said the numbers leaving the party could be even higher, as Labour's systems record active resignations in real time but lapsed memberships only appear in the data after six months.
The leaked data showed total Labour membership at 528,180, down from a peak of 554,000 in July, but still far above the 200,000 members it reportedly had in May 2015.
Official figures are only published in the party's annual report.
A Labour Party spokesman said it was still the largest in western Europe and its members are "one of our greatest assets".
However former PLP chairman Lord Watts told The Times: "I think the tide is turning.
"I imagine people are losing heart because they can see the polls, they're talking to their neighbours and people they work with, and are coming to the conclusion Labour is not doing well and, at this point, not convincing the public."
Reports of a membership slump come after figures showed Labour raised less money through donations than the Liberal Democrats in the last three months of last year.