Jeremy Corbyn has defended reaching out to Republicans at the height of the troubles by insisting he "wanted the violence to stop".
The Labour leader told the BBC One Andrew Marr programme: "I don't want violence, I don't want killing, I don't want all the horrors that go with it."
Mr Corbyn has faced strong criticism for bringing members of the IRA to the House of Commons during the 1980s.
But he told the programme everyone he met had been former prisoners who had completed their sentences and the goal had been to open dialogue and reach a political solution.
Mr Corbyn said: "Yes, I did make myself very unpopular with some people by a preparedness to reach out to the Republican tradition in Ireland, to say ultimately this war is unwinnable by either side, there is never going to be a military (answer) - therefore there has to be a political dialogue.
"At the same time, secretly, the British government was also engaged in that and then eventually in 1994 we got the first ceasefire."
The Labour leader is due to speak at a conference fringe meeting organised by Sinn Fein later today.
Asked if he was less critical of IRA violence than British military action, Mr Corbyn said: "The violence was wrong on all sides and I have said so all along. My whole point was if we are to bring about a peace process, you weren't going to achieve it by military means."
The Labour leader acknowledged his long-running statement for a united Ireland, but added: "Quite honestly, the peace process has brought about a huge step forward.
"There is a lot of cross border agreement, there is a lot of cross border institutions, there is a feeling - you go to Belfast, you go to Dublin, people travel back and forth all the time.
"The Government's are in touch with each other every hour of every day on different issues.
"There is that kind of sense there is one island of Ireland."
Speaking to delegates, shadow Northern Ireland secretary Vernon Coaker said: "Our policy, Labour's policy, is based on a bi-partisan approach built on the principle of consent.
"And as the agreement since 1998 has set out, it is for the people of Northern Ireland to decide their own future and that's how it should be and how it will remain."
He also said: "I will do all that I can to support the ongoing peace process in Northern Ireland, working with all parties and the Irish government. Labour will play its part as it always has done.
"Our party has helped to bring about a substantially better Northern Ireland, but now is the time to move forward, tackling many of the outstanding issues arising from the different traditions and competing narratives, as well as legacy issues around victims, mental health, economic insecurity and poverty.
"The Stormont House Agreement seeks to address some of the most difficult and challenging issues in Northern Ireland. It doesn't hide from them, it sets out practical ways to tackle them and when difficulties arise, let us not criticise but let us encourage and support.
"The British and Irish governments still have a huge role to play in this process as co-guarantors of the Good Friday Agreement."
In a message to people living in Northern Ireland, Mr Coaker said: "The rest of the UK still cares and we do want you to succeed."
Mr Corbyn withdrew from the Sinn Fein-organised fringe meeting, citing the difficulties of attending such events due to the diary demands he now faces as leader of the party.
Mr Coaker replaced the Labour leader and warned against people being "castigated" for saying they support a united Ireland as the Good Friday Agreement allowed for opposing views and aspirations.
Responding to a question, he told delegates: "I think the way I put it is that (shadow chancellor) John McDonnell was right to apologise and he did ... I think there's a better understanding actually of British-Irish relations than what's been happening, that's developed over the last 15 years since the Good Friday Agreement.
"So I'm a bit more optimistic, if you like, I think people get it a bit more than they did.
"I think what is difficult is that the understanding has to be that in Ireland there are competing narratives and there's a nationalist and unionist tradition, particularly in Northern Ireland, and so those traditions will have a different view of the same event.
"I think we have to be very careful about somebody saying, 'I'm in favour of a united Ireland', and then that actually being something they're castigated for, because in the Good Friday Agreement the brilliance of it was to say it's a perfectly legitimate view to aspire towards a united Ireland as it is a perfectly legitimate view to aspire to keep Northern Ireland part of the United Kingdom."
He said different parties in Northern Ireland had recognised that, adding: "That's why the principle of consent is absolutely fundamental to that agreement."
Mr Coaker also said: "If you pick back over every single thing somebody has said then it'll be really difficult."