Paddy Hill was one of the Birmingham Six, who were handed life sentences for the attacks in 1975, before their convictions were quashed in 1991.
He told local paper the Birmingham Mail that the IRA had claimed five people had been responsible and that two had received so-called "comfort letters". Another two are understood to have died.
Nobody has been brought to justice for the incident which killed 21 people and injured 182 others.
Brian Hambleton, who lost his 18-year-old sister Maxine in the IRA attacks, has reacted angrily to claims that suspects could have received letters.
He was also critical of remarks from former Northern Ireland Secretary Peter Hain who said that pursuing Troubles crimes "seems a waste" and that Tony Blair's government acted "honourably" over on-the-runs.
"It leaves me angry (at) these people in power, this just shows their ineptness," he commented.
"We've been lied to from day one because the government and West Midlands Police don't want the can of worms opened, but they'd like to throw the can in the bin, but it's too late now.
"If they had told the truth in the first place, none of this would have come out."
I live the horror every day. Until the day I die I will fight for justice for my sister and the other 20 innocent people who were wiped out that night.
Mr Hambleton called for the local police to reopen the investigation into the blasts.
It emerged last week that 187 letters were issued to republicans, including 38 since 2010.
The details came out following the collapse of the case against Co Donegal man John Downey, who had been charged over the 1982 Hyde Park bomb which killed four soldiers.
The 62-year-old walked free from the Old Bailey because he was sent a letter wrongly telling him that he was not wanted over any crimes - despite an arrest warrant having being issued by the Metropolitan Police.
This prompted DUP First Minister Peter Robinson to give Westminster an ultimatum - respond to what he branded "a crisis" for Northern Ireland in 24 hours or he would resign.
Prime Minister David Cameron responded by announcing a judicial review into the Northern Ireland Office (NIO) scheme on Thursday.
Secretary of State Theresa Villiers also clarified that OTRs who have received letters will not avoid questioning or prosecution if evidence emerges in the future.
Families whose loved ones were shot dead by paratroopers on Bloody Sunday in Londonderry have been left reeling over Mr Hain's suggestion that the soldiers should not be prosecuted if a line was to be drawn on the past.
Mickey McKinney, who lost his brother William at the 1972 civil rights march, said his comments were "outrageous".
"It took us 40 years to come to the end of an inquiry for Lord Saville to say that our people were unjustifiably killed," he said.
"Because there is a police investigation being held into those events to hopefully bring those people to court, Peter Hain and some people in the unionist community complain about it, I think it's seriously outrageous and ridiculous.
"The majority of the families are looking for prosecution, why should these people not be prosecuted?"
John Teggart, whose father was killed by the British Army in Ballymurphy in August 1971, has also reacted on the day he and relatives of nine others who died were in Belfast for a preliminary hearing ahead of an inquest into their deaths.
He said he believed anyone who lost a loved one should be entitled to legal redress.
On Monday afternoon, DUP members of the NI Policing Board, along with independent colleagues and a UUP representative on the Board, called for an extraordinary meeting to hold the PSNI Chief Constable and senior officers of the PSNI to account for their role in the OTR administrative scheme.
DUP Group Leader on the Policing Board, Jonathan Craig MLA said: "These are very grave and serious issues at stake and it is essential that the PSNI give a full and accurate account of their role in this saga."