Gerry Conlon, who was jailed for the Guildford pub bombings of 1974, then released after 15 years having had his conviction quashed, outside parliament with his family.
Tony Blair today apologised to the 11 people wrongfully imprisoned for the IRA bomb attacks in Guildford and Woolwich in 1974.
"I am very sorry that they were subject to such an ordeal and injustice," he told members of the Conlon and Maguire families.
"That is why I am making this apology today - they deserve to be completely and publicly exonerated."
Mr Blair had been expected to make the apology in the House of Commons in reply to a question from the nationalist MP Eddie McGrady.
However, the Speaker, Michael Martin, decided not call the Social Democratic and Labour MP to speak during question time.
Arriving at Westminster this morning, Gerry Conlon called on Mr Blair to remove the "stain on the character of British justice" by apologising for his wrongful imprisonment.
Gerry Conlon was one of four people - the others being Paddy Armstrong, Paul Hill and Carole Richardson - arrested in 1974 and wrongfully jailed for an IRA bomb attack on the Horse and Groom pub in Guildford. The blast killed five people - four soldiers and a civilian.
The four prisoners became known as the Guildford Four.
Gerry Conlon's father and members of Annie Maguire's family were also later arrested and jailed for the attack and other bombings in Woolwich, south-east London following confessions extracted by the police that allegedly identified them as being involved.
Relatives of Mr Conlon and his father, Guiseppe, have been seeking a public apology for the miscarriage of justice after a letter from the British government to the SDLP leader, Mark Durkan, privately acknowledged the wrong done to the family. Guiseppe Conlon, who had a history of bronchial problems, died in prison while serving his sentence, in January 1980.
In October 1989 the court of appeal quashed the sentences of the Guildford Four after doubts were raised about the police evidence.
In June 1991, the court of appeal also overturned the sentences on the Maguires and Guiseppe Conlon.
The case was brought to international attention through the Oscar-nominated film In the Name of the Father, starring Daniel Day Lewis as Gerry Conlon and Pete Postlethwaite as Guiseppe.
Day Lewis and the director of In the Name of the Father, Jim Sheridan, have joined thousands of people who have signed a petition on behalf of the Conlon family in recent weeks seeking official recognition from the government that they were innocent.
The Irish prime minister, Bertie Ahern, and Mr Durkan lobbied Mr Blair in Downing Street meetings last week.
Last month, the Northern Ireland secretary, Paul Murphy, signalled that the prime minister would make a public apology to the Conlons.
By just Us posted 10 February 05