It is about the Rupert Murdoch media smearing Labour party leader Jeremy Corbyn as supposedly involved in spying.
The lyrics are:
A disgruntled opposition backbench MP
He will sell you state secrets over tea
An Eastern Bloc spy can bring down the nation
With a little help from Agent Greenfingers
Steals the heart of darling Diane Abbott
The sneaky Trot
Jeremy Corbyn urged to sue Tory MP who accused him of selling “British secrets to communist spies”: here.
Anti-Corbyn ‘spying’ smears are a sign of Tory desperation: here.