The senior lawyer appointed by the government to conduct an inquiry into police pay is at the centre of a row amid accusations his report has misrepresented the views of officers, some of whom, it is alleged, do not exist.

The row threatens to become political after Keith Vaz, chairman of the home affairs select committee, suggested it might summon Tom Winsor, appointed last October by the home secretary, Theresa May, to explain himself.

Winsor is conducting what is described as "the most comprehensive review of police officer and staff pay and conditions in over 30 years". The former rail regulator has told MPs that 60% of officers will be better off as a result of his recommendations, which follow consultations with hundreds of staff.

But in early July the Police Federation asked Winsor to "verify the evidence presented in your report, especially as these comments appeared to directly contradict the views of officers articulated to the Police Federation".

Now, in an explosive letter sent to Winsor and copied to Vaz, the federation says it has discovered some of the officers interviewed by Winsor and his team "do not actually exist and many of those that do have rejected the statements attributed to them". In its letter, which was leaked to the Observer, the federation, which speaks for some 140,000 officers in England and Wales, cites several examples to back up its claims.

These include two officers, purportedly from Kent police, who were named in the report but were not known to the force. The letter says a third officer from Kent quoted in the report "had not spoken to you because he was on holiday".

The letter by Ian Rennie, the federation's general secretary, continues: "Another officer said about the statement attributed to him: 'It was not me … I basically told him I have no money as it is, and asked him not to take any more off me, as I have three children to feed and clothe.'"

The claims threaten to embarrass Winsor and his team, whose findings are crucial to determining the future of policing at a time when there are claims of plunging morale in the force. The federation alleges: "It would appear that you are trying desperately to present a view that officers support and welcome your proposals."

Last month the home affairs select committee issued a report suggesting Winsor should "consult with police more widely before making any further recommendations". Winsor told the committee he had interviewed 200 police officers and staff. His first report identified 69 officers by name and rank. Winsor claimed frontline officers and staff he had interviewed had said morale was low because they were receiving the same pay, and in some cases less, than those in back-office roles.

Vaz expressed shock at the federation's claims. "I was most surprised to see the letter from the Police Federation and their concerns that the evidence that Tom Winsor gave to the select committee contained information that was not accurate. I am sure that the committee will want to look at these matters again and I will be writing today to Mr Winsor to ask him to confirm the evidence he has given. If he does not do so, I will expect him to be recalled by the committee."

A spokesman for the Winsor review said it had consulted more than 200 officers and staff and received 7,100 comments on its website. He added: "Part one of the review of police remuneration and conditions consulted widely with frontline officers and staff. All of the names were given by officers themselves or by their supervisors subsequently. Contrary to what the Police Federation has alleged, the Winsor report does not attribute any statement to any named police officer or police staff member. The report is clear that officers who regularly work unsocial hours and who are using especially critical skills would, in general, earn more under the recommendations, if implemented in full."