UK Labour Party
He has been told to "get back to work" and resolve the long-running pay dispute.
Prime minister branded "out of touch" and a "robotic" programmed "clone".
Writing for HuffPost UK, the Labour leader says the Tories want to "cling to power through a campaign of fearmongering and deceit".
"Thank you Andrew Mitchell, I needed a giggle this morning."
Pro-Jeremy Corbyn campaign group Momentum condemned the party leader's "fiscal conservatism".
Danny Beales said it had "cut us off at the knees" as the Tories clung on by just 495 votes.
The results in Selby and Uxbridge threw up as many questions as answers for Labour.
Angela Rayner blamed the scheme for the Tory win but the mayor insisted it is "necessary to save the lives of young and vulnerable Londoners".
Holding on to Boris Johnson's old seat was a glimmer of light on an otherwise miserable night for the prime minister.
Tensions between the London mayor and Keir Starmer are set to increase after the Tory victory.