She is attending the NATO summit in Brussels along with world leaders including Donald Trump and Angela Merkel, so Cabinet Office Minister David Lidington and Shadow Foreign Secretary Emily Thornberry are standing in.
But that will not stop it being a fiery PMQs session, following huge Brexit developments this week following the presentation of Mrs May’s new plan to exit the bloc on Friday.
The White Paper revelations were followed by the shock resignations of Brexit Secretary David Davis on Sunday night and Foreign Secretary Boris Johnson on Monday, both of whom were strongly opposed to the new plan.
Last night, Conservative vice-chairmen Ben Bradley and Maria Caulfield also resigned in protest.
Mrs May might now have to face staving off a leadership battle, with Tory Brexiteers warning her she has one week to come up wth a new Brexit plan or face a vote of no confidence.
See below for live updates on PMQs:
12:32pm update: “President of our closest ally”
Mr Lidington says Mr Trump was democratically elected and would be welcomed.
He says: “It is right that we welcome the duly elected president of our closest ally as we shall do tomorrow.”
12:30pm update: Criticism of Donald Trump’s visit
Scottish National Party MP Ian Blackford attacks the Government’s red carpet treatment planned for Mr Trump’s visit.
He says: “From the public the welcome will be far from warm.
“With protests planned against President Trump’s policies and dangerous rhetoric, will the minister follow the SNP’s lead and challenge President Trump on his abysmal record on human rights, his repugnant attitude towards women and his disgusting treatment of minorities.
“Or does the minister think he will simply follow the Prime Minister’s lead and join the president hand in hand?”
12:24pm update: Fighting violent crime
Conservative MP Andrew Rosindell implores the Government to step in and help stop the rise in violent crime sweeping across London.
He accuses Mayor of London Sadiq Khan of not doing enough to make the capital safe.
Mr Lidington responded: “It takes action to stop these crimes, not just a press release from the Mayor’s office.
“That is what this government is undertaking. “
David Lidington and Emily Thornberry are attending Prime Minister’s Questions
12:22pm update: “Dog’s Brexit”
Ms Thornberry accuses Mr Lidington of supporting “a dog’s Brexit”.
She says: “It will satisfy nobody, will not fly in Europe, will waste the next few weeks.”
12:20pm update: “No grip on reality”
Ms Thornberry claims the Chequers agreement shows “no grip on reality”.
She blasts: “Do what I urged him to do two years ago – instead of trying to negotiate some half-baked back door version of the customs union, get on with negotiating the real thing.”
Mr Lidington responds: “The party opposite said they would strike new trade deals but their plan to stay in the Customs Union prevents that.”
He then accuses the Labour party of considering a second EU referendum.
12:14pm update: Chequers agreement clash
Emily Thornberry and David Lidington are clashing on the controversial Chequers agreement outlined last Friday.
Ms Thornberry says: “He cannot admit the truth! The truth is the Chequers proposal is total delusion.
“The UK cannot set its own tariffs on goods and keep frictionless trade with the EU. The technology to do so doesn’t exist.
“It is a customs union in all but name, but it does not cover our service industry.
“Can I ask the Minister of State to explain why a country like China would agree to import more of a services if it cannot change tariffs on its goods?”
Mr Lidington accuses Ms Thornberry of misunderstanding the White Paper.
David Lidington accused Labour of considering a second EU referendum
12:11pm update: Britain in “turmoil”
Ms Thornberry continues to come out with all guns blazing, picking up on Donald Trump’s comments yesterday that Britain was in “turmoil”.
She says: “Even Donald Trump thinks they’re in turmoil and he hasn’t even got to Britain yet!”
Ms Thornberry then slates the Government as “Reservoir Dogs remade by the Chuckle Brothers”.
Now onto Brexit: “Can he explain how frictionless trade is going to be made under this Government’s Chequers plan.”
12:09pm update: ‘Flag-gate’ incident
David Lidington gets the first dig in by offering Emily Thornberry an England flag – a cheeky nod to the Shadow First Secretary of State’s Rochester ‘flag-gate’ incident.
He wishes “the boys” good look ahead of England’s World Cup semi final against Croatia this evening.
Ms Thornberry also wishes the team the best of luck for “this match and hopefully the final on Sunday”.
She then pokes fun at Theresa May, saying the national team shows how well things can go “when everyone respects and listens to the manager”.
Ms Thornberry asks Mr Lidington what the England team can teach “this shambles of a government”.
She also sends her best wishes to the England football team for their World Cup semi final against Croatia tonight.
12:03pm update: Tributes
David Lidington and Emily Thornberry begin by paying tribute to Lord Carrington, who died aged 99.
He was the last survivor of Winston Churchill’s post-war Government.
They also commend the “incredible efforts of authorities in Thailand in the successful rescue operation”.