Ken Boston quit in the wake of the fiasco over last year's Sats tests
The English qualifications agency's former head, who quit over last year's Sats fiasco, has described ministers' version of what happened as "fiction".
Ken Boston claimed ministers had incorrectly portrayed him as complacent about marking failures that affected thousands of children.
Dr Boston is giving evidence to a committee of MPs.
The government says Dr Boston should take any complaint to Lord Sutherland, whose inquiry blamed his organisation.
Dr Boston, former head of the Qualifications and Curriculum Authority (QCA), has told MPs that the remit of Lord Sutherland's inquiry had been structured in a way that put a "protective fence" around ministers.
The Tories say Schools Secretary Ed Balls owes everyone an apology.
This latest war of words over the failures by test contractor ETS Europe has been prompted by a letter from Dr Boston to the Commons children, schools and families select committee.
Dr Boston tendered his resignation ahead of Lord Sutherland's report last December.
Lord Sutherland laid the blame at the door of ETS - but also blamed the QCA - for having "failed its remit".
The QCA disbanded its assessment agency but refused to accept Dr Boston's resignation, pending its own inquiry.
It finally did so only on 1 April, saying it was deeply grateful to him for his significant and lasting contribution to education reform.
According to extracts of his letter to the select committee, Dr Boston rejected what he said had been attempts by ministers to portray him as "complacent and disengaged".
He said that in evidence to Lord Sutherland's inquiry that Schools Minister Jim Knight had wrongly claimed he (Dr Boston) had been present at one meeting last June when the Sats tests were discussed - when he had not even been invited.
In a statement, the Department for Children, Schools and Families (DCSF) said Mr Knight had already written to Lord Sutherland, and to select committee chairman Barry Sheerman, admitting his error on this issue.
"Lord Sutherland was clear in his response that this made no difference to his findings," a spokesman said.
Lord Sutherland said his report had concluded that within the QCA there had been "insufficient corporate oversight" at executive and board level.
The DCSF spokesman added: "If Ken Boston believes a further correction is required then he should raise it with Lord Sutherland who carried out the independent inquiry."
Dr Boston also challenged the inquiry's finding - read out by Mr Balls in the Commons - that ministers had "usually pressed" him for answers about the Sats marking problems and that the QCA had given "strong reassurances" that the tests were on track.
"This too is fiction," he said.
'Far from the truth'
"I was not asked to meet directly with the schools minister in the months leading up to the delivery failure at the end of June, including the critical marking period in the final eight weeks.
"Nor was I being 'pressed' by ministers for answers on the telephone or by e-mail," Dr Boston wrote.
"The flawed evidence... has been used to portray me as complacent, disengaged, and constantly beleaguered by ministers with questions I was unable to answer," he said.
"This is far from the truth; it was not corrected by ministers or DCSF officials at draft report stage; and it has been used by ministers to my serious disadvantage."
Shadow schools secretary Michael Gove said ministers had concentrated on blaming others instead of saying "sorry".
"Ed Balls owes the teachers, parents and children who were let down by his deliberate failure a profound apology and he must come to the House of Commons to set the record straight."