"More than 17,000 Labour members have quit the party in the past three months as disputes over antisemitism and Russia erode Jeremy Corbyn’s support base.

The Times understands that internal membership figures show the party has lost about 3 per cent of its paying supporters since the start of the year. Last week hundreds of members resigned from the party and more than 3,000 did not renew their direct debits, insiders said."

I only go by what they say.
The Independant:
Labour’s membership reached a peak of 570,000 after the general election but now appears to be falling.

According to the leaked report, no region in England reported a rise in party members since the start of 2018. London lost 3,500 members in the past three months, and the North-west reported a fall of 2,000.

Meanwhile the Corbyn-supporting campaign group Momentum has claimed that it is gaining members.(they would, wouldn't they!)
I have not the slightest interest in why they have quit, perhaps they feel it is a total waste of money.Why they would quit over novichok totally escapes me. Labour did not issue this pack of lies, they over exerted themslves with WMD and dragging us into the Gulf War.
Anyway watching Labour attempt self destruction makes for prime time comedy as far as I am concerned.
The sooner the blight of corbyn toddles off down the road the better.