Police Ombudsman Nuala O'Loan has rejected allegations that her report into collusion was "error riddled".
The Royal Ulster Constabulary was replaced in 2001
A group representing more than 3,000 retired police officers published a critique of her report and demanded she apologise.
Her report found Special Branch had colluded with UVF members in north Belfast who killed up to 16 people.
A special debate on the findings of the report will be held in the House of Commons later.
On Tuesday, the Retired Police Officers' Association, claimed her report was riddled with basic errors of fact and judgement.
The body includes former Special Branch officers criticised by the ombudsman.
Speaking on Radio Ulster on Wednesday, Mrs O'Loan said her report was "soundly evidence based" and that she was standing by it.
"A number of retired officers did assist the investigation," she said.
"They answered difficult questions, they answered them honestly and the findings of the investigation arrive from information received from police officers - serving members, retired members - police documentation.
"It is a very, very soundly evidence-based report and I stand absolutely by my findings."
Nuala O'Loan rejected the criticism
Members of the association spent the past two months writing their own paragraph by paragraph response to the document published by Mrs O'Loan.
In it, they accuse the ombudsman of misusing the word "collusion" in a way which had led to it being used as "a political catchphrase".
They said police officers who served their country were being vilified in the court of public opinion.
The association has sent a copy of its report to the secretary of state and is demanding a public apology from Mrs O'Loan for what it said were unfounded allegations.
The ombudsman's report is also expected to be discussed in a debate in the House of Commons on Wednesday.
The Police Ombudsman found UVF members in north Belfast committed murders and other serious crimes while working as informers for Special Branch.
She found that Special Branch officers had given the killers immunity.