Boris Johnson has been accused of sacking a senior Education official as a 'scapegoat' to protect Gavin Williamson.
It emerged this afternoon the Prime Minister had fired Jonathan Slater, the most senior civil servant at the Department of Education over the A-level results fiasco.
His departure comes a day after the resignation of Ofqual CEO Susan Collier over the debacle.
But the PM was accused of using civil servants as 'political pawns' to shield ministers from accountability.
Dave Penman, head of the FDA Union, said: “If it wasn’t clear before, then it certainly is now – this administration will throw civil service leaders under bus without a moment’s hesitation to shield ministers from any kind of accountability.
"Those who have dedicated their lives to public service are being discarded without hesitation to keep scrutiny from the government’s door."
Mr Slater is the fifth senior civil servant to lose his job since Mr Johnson came to power, following Cabinet Secretary Sir Mark Sedwill, Foreign Office Permanent Secretary Sir Simon McDonald, Ministry of Justice Permanent Secretary Sir Richard Heaton and Home Office Permanent Secretary Sir Philip Rutnam.
The Department for Education announced that its permanent secretary, Mr Slater will stand down because "the Prime Minister has concluded that there is a need for fresh official leadership".
Mr Penman added: "Whilst the origins of the exams fiasco may be complex, the solutions for this government are simple: scapegoating civil servants. Ministerial accountability is dead and the message to civil servants is that they are expendable the moment life gets tough for a minister.
“After this government’s continuous anonymous briefings to the press, trust between ministers and civil servants is already at an all-time low and this will only damage it further. No private sector company would treat their leaders this way and still expect to succeed. At a time when the country needs the civil service like never before, the government is happy to tarnish its reputation and throw away years of experience and expertise.”
Mr Johnson was already facing a backlash after blaming a "mutant algorithm" for the exam results disaster.
Labour accused Mr Johnson of trying to avoid taking responsibility for a "shambles" caused by his Government's "incompetence".
The Prime Minister, addressing pupils at a school in Coalville, Leicestershire, acknowledged that the situation had been "stressful" for those awaiting A-level and GCSE results.
"I'm afraid your grades were almost derailed by a mutant algorithm," he told them.
"I know how stressful that must have been for pupils up and down the country.
"I'm very, very glad that it has finally been sorted out."
Mr Johnson had previously claimed that the algorithm-based grades would be "robust" and "dependable".
Shadow education secretary Kate Green said: " Boris Johnson is shamelessly trying to avoid taking responsibility for the exams fiasco that his government created.
"Responsibility for this shambles lies squarely with Downing Street and the Department for Education, who set out how they wanted the algorithm to work and were warned weeks in advance of issues, but repeatedly refused to address the problems they had created.
"It is this Tory government's incompetence that is to blame for the exams fiasco."
Kevin Courtney, joint general secretary of the National Education Union, said: "It is brazen of the Prime Minister to idly shrug away a disaster that his own Government created.
"Parents, students, teachers and heads will be horrified to see the leader of this country treat his own exams fiasco like some minor passing fad.
"The public will not easily forget the emotional rollercoaster of this year's results season. It is certain to put a long-lasting dent in the Government's reputation on education."
Education mandarin Mr Slater will stand down on September 1, in advance of the end of his tenure in spring 2021.
Susan Acland-Hood, currently interim second permanent secretary, will take over as acting permanent secretary.
Labour frontbencher Bill Esterson said "the buck stops" with the Education Secretary.
"First the head of the regulator Ofqual resigns over the exam fiasco, now the permanent secretary at the Department for Education," he said.
"Why is the secretary of state still in post? Two scapegoats can't save him.
"The buck stops with Williamson. Sooner or later, he has to go too."