Corbyn's aide Andrew Murray, a member of the Communist Party until his conversion to Labour in 2016 (!) says that MI5 is behind his not getting a Commons security pass, and leaking the fact that he is banned from Ukraine as a Putin stooge.

Tom Watson is not convinced.
Guardian,
"Asked whether he believed the intelligence services were seeking to undermine Labour, Watson said: “I’m assuming they don’t, but if Andrew Murray has more evidence then he should provide it.”
There was a notably ruder response from Ben Wallace, the security minister in the Home Office.
He tweeted: “Oh dear. Sorry to pop the vanity of your own self-importance Andrew but our spooks don’t waste their time pumping out stories to the Mail on Sunday about someone no one has ever heard of. They are too busy trying to stop terrorism & Russian assassination attempts.” "
https://www.theguardian.com/politics/2018/sep/20/tom-watson-says-deep-state-claim-by-corbyn-aide-a-bit-john-le-carre