The pair will go head-to-head after the prime minister suffered three new devastating blows which threaten to kill off any hopes the Conservatives can avoid a general election defeat.
It has also emerged that several Tories - including business secretary Kemi Badenoch - are in a WhatsApp group called the “Evil Plotters.”
Meanwhile, in a deeply embarrassing development for Mr Sunak’s Brexiteer credentials, it emerged that the UK population is set to rise by another 6.6 million by 2036.
With the prime minister on the rocks, Sir Keir could stick the boot in during PMQs again this week, after a bruising battle at the despatch box last week.
Mr Sunak, meanwhile, could attack Labour after Rachel Reeves claimed the party will not scrap Liz Truss’s decision to lift the cap on bankers’ bonuses.