Keir Starmer today blasted "weak" Rishi Sunak for striking a “grubby deal trading national security” to save his own job.
Labour’s leader accused the new PM of offering Suella Braverman her Home Secretary job in exchange for the right-winger's key support in the Tory leadership contest.
In a bid to form a unity Cabinet, Mr Sunak brought Ms Braverman back six days after she resigned for a security breach.
Cabinet Secretary Simon Case - the head of the civil service who found two breaches of the ministerial code last week - is “livid and very concerned”, according to The Times.
Questioned at a raucous PMQs today, Mr Sunak refused to say if officials had raised concerns about the appointment.
Labour's leader replied: "We can all see what’s happened here. He’s so weak he’s done a grubby deal trading national security because he was scared to lose another leadership election.
"There’s another Tory at the top but it’s always with them party first, country second.”
Labour today wrote to Mr Case demanding "a full investigation into the security breaches by the Home Secretary, including the warnings given to the Prime Minister."
Shadow Home Secretary Yvette Cooper said: "Given the Prime Minister’s decision to reappoint her to the Cabinet post overseeing national security, it is vital for the public to have transparency on what occurred."
In a dig after Ms Braverman left the chamber, leaving minister Jeremy Quin to answer questions on her appointment, Ms Cooper said the Home had "run away from basic accountability to this House".
She said: "It is the same old Tory chaos and it is letting the country down."
SNP Westminster leader Ian Blackford said it was a “sleazy back room deal to shore up his own position”, adding “this is a return to the sleaze and scandal” of governments past.
The PM's official spokesman said he "didn't recognise" claims Mr Case was "livid". But he refused to say what amount of angry he was, or deny that he had raised concerns with the Prime Minister.
“I don’t as standard get into discussing advice PM or ministers receive from officials," the spokesman said.
Downing Street confirmed Mr Sunak will "shortly" appoint an independent advisor on ministerial interests - a job that has been vacant since the days of Boris Johnson.
But the PM's spokesman was unable to say if the advisor will be asked to investigate Ms Braverman, or allowed to initiate investigations of their own accord.
The PM's Press Secretary claimed the Home Secretary job was first discussed with Ms Braverman "yesterday when she came into Downing Street".
Meanwhile, the PM’s press secretary announced he will U-turn on Liz Truss's decision to lift the fracking ban, and impose a "moratorium" that was in the Tories' 2019 manifesto.
But she repeatedly refused to say he’s committed to “all” the promises in the 2019 manifesto. Instead she said: “He’s committed to delivering on the promise of the manifesto”
And she refused to say he would raise benefits OR pensions in line with inflation next April - despite Mr Sunak previously promising both, and Liz Truss committing to the pensions triple lock days before she quit.
No10 also put Liz Truss's commitment to spend 3% of GDP on defence by 2030 in doubt - despite a minister, James Heappey, saying he will resign if it is broken. Downing Street said it will only be spelt out in the November 17 Autumn Statement.
But No10 confirmed the Energy Price Guarantee - which caps bills at an average of £2,500 a year - will last through to the end of March.
No10 also said Mr Sunak will move his multimillionaire family into Downing Street - and live in the smaller No10 flat they lived in before, not the larger No11 flat Prime Ministers have used for years.
Elsewhere in PMQs, Mr Starmer pointed to comments Mr Sunak made in the summer leadership contest about too much funding going to "deprived urban areas".
Labour's leader said: "In public he claims he wants to level up the north but then he boasts about trying to funnel vital investment away from vital areas. He says one thing and does another!"
Demanding the Tories call an election he said: “The only time he ran in a competitive election he got trounced by the former Prime Minister, who herself got beaten by a lettuce.”
Mr Sunak hit back: "I'm the first to admit mistakes were made and that's the reason I'm standing here. But that is the difference between him and me.
"This summer I was being honest about the difficulties that we were facing, but when he ran for leader he promised his party he would borrow billions and billions of pounds.
"I told the truth for the good of the country, he told his party what it wanted to hear. Leadership is not selling fairy tales, it is confronting challenges, and that is the leadership the British people will get from this Government."
Meanwhile, after a Cabinet meeting this morning, Mr Sunak delayed the government's much-anticipated October 31 fiscal statement - which is expected to unleash a new wave of Tory austerity - until November 17.
It has also been updated to a full Autumn Statement, the most important event outside a Budget.
Mr Sunak warned there will be “difficult decisions to come” in his first speech in Downing Street but faces an avalanche of warnings and potential Cabinet clashes.
He has appointed Mel Stride, who warned against cutting benefits, to lead the welfare department and Andrew Mitchell, who has slammed foreign aid cuts, as Development Minister.
And last night he did what Liz Truss never bothered to and rang Scottish First Minister Nicola Sturgeon - who waned him not to cut public services. Ms Sturgeon said she voiced “my fear that further austerity will do real damage to people and public services.”
Iain Porter of the Joseph Rowntree Foundation urged Mr Sunak to “move quickly” and pledge benefits will rise by 10.1% inflation in April - as he had promised when he was Chancellor.
“Families on low incomes desperately need stability and certainty, as they try to afford the essentials, pay their rent, and keep food on the table,” Mr Porter said.
During his first Tory leadership campaign, Mr Sunak boasted to Conservative members in Tunbridge Wells, Kent, how as Chancellor he moved money from hard-up communities to wealth shires and towns.
“I managed to start changing the funding formulas, to make sure areas like this are getting the funding they deserve because we inherited a bunch of formulas from Labour that shoved all the funding into deprived urban areas and that needed to be undone,” he claimed.
“I started the work of undoing that.”
