Gerry Fitt, the first leader of the Social Democratic and Labour Party (SDLP), died in England this afternoon.
The 79-year-old had been in poor health for some time.
SDLP Leader Mark Durkan expressed his deep sympathy for the family of Gerry Fitt. Mr Durkan said Mr Fitt was a key figure in the civil rights movement and in the political life of Northern Ireland for many years.
An Taoiseach, Bertie Ahern, said Lord Fitt was often in the front line of the Troubles but practised the message of moderation and tolerance that he preached.
A native of Belfast, Mr Fitt once worked as a barber's assistant and served in the British Merchant Navy for the 12-year period from 1941 to 1953.
He was elected to Belfast City Council and first won a Belfast City Council seat in 1958 as an Irish Labour member.
In 1966, he took the West Belfast Westminster seat from the unionists and began to raise civil rights issues in the House of Commons.
He was a founder member and first leader of the SDLP in 1970.
I973 was the high-point of his political career when, as SDLP leader, he signed the Sunningdale Agreement and became Deputy Chief Executive to Brian Faulkner in the power sharing executive at Stormont.
It collapsed the following year and he subsequently insisted that unionists had been pushed too hard on all-Ireland structures.
He resigned from the SDLP in 1979 over policy differences. He criticised the hunger strikes in 1981 and lost his City Council seat that year to the SDLP's Brian Feeney.
He was an outspoken critic of the IRA during the early 1980s and was attacked in his home by republicans. He lost his Westminister seat to Sinn Fein's Gerry Adams in the I983.
The following month he was appointed a life peer by Margaret Thatcher and Michael Foot as Lord Fitt of Bell's Hill. His return visits to Belfast were limited.