Sources in Belfast named the chief republican as Martin McGuinness, a leading member of Sinn Fein who was recently accused of being a key IRA figure.
Republican sources claim documentary evidence of the talks, said to have come to an end in June. This raises the possibility that contacts were opened following the IRA's Bishopsgate bomb which devastated the City of London on 24 April.
Labour's Northern Ireland spokesman, Kevin McNamara, said last night he understood a senior Conservative met Mr McGuinness with the knowledge of the Government. Asked on Radio 4's The World Tonight if he knew who the politician was, Mr McNamara said: 'There are no names given out yet. But presumably if this matter is going to be pursued and pressed, Sinn Fein will have to say who he was or keep quiet.'
The Sinn Fein leader, Gerry Adams, said yesterday the position of John Major was 'inconsistent and hypocritical in view of the prolonged contact and dialogue between his government and Sinn Fein, which occurred without preconditions.' The claim that talks had taken place was supported by Ian Paisley and the SDLP deputy leader, Seamus Mallon.
Mr McGuinness, who served several jail sentences for IRA membership in the 1970s, is said to have had a series of meetings with civil servants and exchanged documents. Mr McGuinness and Mr Adams are regarded as the key figures in the republican movement. This year Mr McGuinness was arrested and questioned about alleged IRA activities.
Republicans claimed the Prime Minister stopped the dialogue under pressure from Ulster Unionist MPs whose support he needed to win the vote on the Maastricht treaty.
In Dublin, the Taoiseach, Albert Reynolds, declined to answer directly a question on whether he had had indirect contact with republicans. He replied: 'No week passes that I do not have people from both communities keeping me informed as to their views.' Such developments have led to widespread speculation that the Hume-Adams talks process, far from being the main avenue of political talks with republicans, may have been only one part of a web of contacts.
Meanwhile, the Prime Minister's Guildhall speech on Monday is seen as having helped to bridge a developing gap between London and Dublin. The two governments are seen to have moved somewhat closer on whether inter-party talks should occupy centre stage. But Mr Major has declined to endorse the process which the Taoiseach hopes could lead to a cessation of IRA violence.
One Conservative source suggested that Mr Major might be on the point of launching an initiative aimed at becoming the prime minister who brought peace in Ireland. Unionist sources remained convinced that Mr Major would do nothing to jeopardise their support in the Commons.
The Archbishop of Canterbury, Dr George Carey, said yesterday that compromise should not be seen as a sign of weakness, adding: 'This is a time for all people of goodwill to be willing to contemplate bold approaches and movement from entrenched positions for the sake of those in Northern Ireland who have carried the burden of violent death and suffering for so long.'
The republic's opposition Fine Gael leader, John Bruton, said: 'There is no excuse now for the IRA to continue killing people. The British Prime Minister has said that they have a place at the table if they are willing to stop killing fellow Irish people.'
Sir Patrick Mayhew, the Northern Ireland Secretary, said on Radio 4's Today that Sinn Fein could be at the negotiating table within six months. He implied that a Democratic Unionist veto on such talks would be unacceptable.
President Bill Clinton had an unscheduled meeting yesterday with Dick Spring, the Irish Foreign Minister. The White House meeting is a sign of US interest in peace moves because Mr Clinton seldom meets foreign ministers.