A former press officer for the IRA hunger strikers in the Maze has claimed that Margaret Thatcher's offer of concessions to end the fatal 1981 strike supports his assertion that some of the republicans' external leaders vetoed the deal.

Richard O'Rawe said the release this week of secret government papers from the period bolstered his claim that the prime minister had sanctioned a deal that could have ended the hunger strike earlier and saved the lives of up to four IRA and two INLA prisoners.

The documents have triggered a fierce debate within republican ranks over the precise sequence of negotiations conducted through a secret, MI6-operated channel of communication between the IRA and Downing Street.

Danny Morrison, one of the key Sinn Féin figures at the time, has claimed the newly declassified documents vindicate the IRA's decisions because they show that the British government had not formulated a final position.

O'Rawe has been vilified in his native west Belfast over his allegations that a compromise was put forward by go-betweens that would have given the republican prisoners most of their five demands inside the top security jail.

The prisoners began the hunger strike to win political status and had five core demands, including not wearing prison uniforms as well the right of freedom of association on the H-Blocks. O'Rawe maintains that the 1981 papers provide fresh evidence that an offer was on the table in early July that would have been acceptable to the republican inmates in the Maze.

In the papers the go-between is codenamed "Soon" but has since been revealed to be the Derry businessman Brendan Duddy. Speaking at his west Belfast home on Friday, the former IRA spokesman in the H-Blocks said: "This was all confirmed in Duddy's own papers last week [to the University of Galway] and now these archives from Kew confirm the same thing – there was an offer.

"There is no doubt about that now that on 5 July the British met the majority of the prisoners' demands, which the prisoners accepted and Duddy has already accepted that to be the case."

O'Rawe added: "Even the IRA army council was not told about this offer. These papers from Kew confirm and reinforce Duddy's papers released to the University of Galway. In my opinion there was a secret cabal outside of the army council that vetoed the offer.

"They [certain republican leaders] played hardball with the Brits and the Brits called their bluff. In that period Joe McDonnell died. Was this stupidity or cynicism? Did they want Owen Carron elected as Bobby Sands's successor or were they thick as champ? On 5 July that should have been it, over – the prisoners should have had the final say – but these guys on the outside cut us out. Even Thatcher had been prepared to offer a deal, as these papers prove today."

For more than 20 years Duddy acted as a secret intermediary between the government and the IRA through his contacts with the MI6 officer Michael Oatley. The files released from the Kew archives include a log of a series of frantic telephone calls between Soon and his MI6 contact in the days leading up to the government's offer. In one call Soon explained the IRA's demands. "Immediately following the ending of the hunger strike, concessions would be required on clothes, parcels and visits. This, he said, would provide the Provisionals with a face-saving way out," the log noted.

Others on the IRA army council in the summer of 1981 have confirmed they were not made aware of the offer and that a secret group based in Belfast took control of the negotiations in July. Ruaraigh O'Bradaigh, who would go on to break from Sinn Féin and form the hardline Republican Sinn Féin five years later, said he had been on the IRA army council during the hunger strike but had been kept in the dark about the British offer.

Morrison told the Guardian earlier this week: "We never got the final position [before] Joe McDonnell [the fifth hunger striker] died. O'Rawe has written in his book that the republican leadership allowed McDonnell to die to [build political support and] get Owen Carron elected [as MP].

"But the writ for the Fermanagh byelection wasn't moved until 20 July, some time after McDonnell died. O'Rawe's book spends four pages saying what never happened."

The Northern Ireland historian Dr Eamon Phoenix, writing for the BBC, disputed O'Rawe's interpretation. "These documents show that the prospects of an early deal to end the hunger strike evaporated over that July weekend," he said.

"The British never actually formulated their final statement while concessions were strongly opposed by senior NIO [Northern Ireland Office] ministers, led by Humphrey Atkins.

"This seems to contradict the former H Block prisoner Richard O'Rawe's claims in his book of a clear British offer around 5 July."

Professor Paul Bew, a leading expert on the history of the Troubles, said: "Some people will want to see this as proving O'Rawe's thesis, but given the chaos of the time it's difficult to go that far. It clearly does not disprove his thesis."

• This article was amended on 9 January 2012 to correct the spelling of the name of Joe McDonnell.