President Mary McAleese, who first met Brian Lenihan as a student at Trinity College, said the death of such a young and talented politician was untimely.
As minister for finance, Brian had to confront challenges, the scale and gravity of which were unprecedented in the history of the state," she said.
"Despite his illness, he faced up to those challenges with extraordinary but characteristic dignity, courage and good humour. Brian's death is an enormous loss to public life in Ireland."
The president said she hoped the Lenihan family could draw some comfort knowing the former minister lived a life of outstanding personal integrity and dedicated public service.
Taoiseach Enda Kenny, at a meeting of the North South Ministerial Council in Farmleigh, Dublin, described Mr Lenihan as a decent man and exemplary public servant.
"Brian Lenihan was exemplary in the carrying out of his public duties. He continued a long line of representation for Ireland in public life by both his father (Brian) and grandfather (Patrick) and his family in general," he said.
"He exemplified a great sense of humanity in the public representation he gave."I'd like to say I've known Brian Lenihan for many years and regard him as a friend in politics."
Mr Kenny said that even though he differed politically with Mr Lenihan he was always available to discuss political matters.
"He exemplified wonderful courage of an enormous extent in speaking publicly about the illness that he challenged so courageously and about the difficulties he was encountering personally in dealing with that illness and in carrying out his public duties in the most challenging circumstances for any minister for finance."
Former Taoiseach Brian Cowen said all of the tributes were an indication of the esteem in which he had been held and his sympathy was with his wife and family today.
“Brian was very able in the job and continued to be able in the job. He was an extraordinary individual with a wonderful philosophy on life,” he said. “He had a great sense of public duty and public service... he sought to serve this state in the most difficult of circumstances. His intellectual capacity was second to none.”
Former Taoiseach Bertie Ahern said: "He was a politician of outstanding capabilities and compassion who was colourful and extraordinarily clever. He did immense work on behalf of the people of this country as a minister and his loss is a huge one for Irish politics."
Mr Lenihan’s former cabinet colleague and former Tanaiste Mary Coughlan said that it was a very sad time. “He could absorb a brief in a very short time. He was selfless in that he put the country first before himself. We shouldn’t forget the man either, he was convivial and charming, he loved people, he was wonderful company, and a great story teller. His illness was something he really took by the scruff of the neck. We used to worry about the fact that he was doing too much.”
Fianna Fail TD Pat Carey described Mr Lenihan as "an extraordinary person", and recalled that only three weeks ago, when he was clearly unwell, he had turned up to a Fianna Fail function in Dublin and stayed until 3am, talking to everyone.
"He found detail tedious sometimes," he said, "but once he was doing the job, he knew all about the detail.”
Martin Mansergh told RTÉ he was “devastated by the news” and said: “I knew in the last two or three months he wasn’t particularly well. It’s come as a shock.
“He shouldered the burden from 2008 through to earlier this year of trying to protect this country as best as was possible from the fallout from a crisis which no one claimed he had any part in creating. He showed huge political courage once his illness became apparent.”
Speaking to Kildare FM, Fianna Fáil TD Sean Ó Feargháil paid tribute to Mr Lenihan’s lengthy battle with his illness: “He was a man of enormous bravery and great courage on a human level. Anyone else in that situation would have focused on treatment and recovery, and yet Brian Lenihan threw himself into the enormous task of managing the country’s finances.”
Former Minister for Tourism and Sport and Fianna Fáil colleague, Dr Jim McDaid told Highland Radio: “No matter what you said about Fianna Fail, Brian Lenihan was someone who had the admiration of the public in general and he did certainly play his part in whatever he had to do. He was always that type of person that was ready to put his neck on the block.”
His constituency colleague, Sinn Féin TD Paul Donnelly said that Mr Lenihan’s passing had come as a huge shock: “He was a giant in Irish politics and commanded respect from across the party divides.”
Northern Ireland’s First Minister Peter Robinson said: "He was a good friend to Northern Ireland. He never sought any concession for his illness, he came and did a full day's work and more."
Sinn Fein president Gerry Adams described Lenihan as a "man who was very popular across the political divide and was much loved in his constituency and across the state."
The chief executive of Chambers Ireland, Ian Talbot, said: "Brian Lenihan showed his unwavering commitment to the Irish public and his constituents by working through his illness."
On Twitter Independent TD Shane Ross described Brian Lenihan as "probably the finest parliamentarian of his generation. And one of the nicest, most generous people in the Oireachtas.”
EU economics commissioner Olli Rehn said Mr Lenihan’s personal and professional contribution to addressing Ireland’s economic difficulties meant he would be held in the highest esteem by those who worked with him in Europe. His loss would be shared by many people “across the political spectrum in Europe, who had the honour to know Brian Lenihan as a politician and as a person”.
“He put his duty to the nation above his personal difficulties, Brian Lenihan has provided us with an outstanding example of public service,” Mr Rehn said. “Brian displayed great personal courage, strength and dedication to the public good, during a period of exceptional economic challenge in the life of Ireland and Europe.”
The former Green Party leader John Gormley, who served in the same cabinet as Brian Lenihan said "history will be kind" to the former finance minister. "It will show that he was an excellent finance minister."
On a personal level he described Mr Lenihan as "kind and decent". He acknowledged that there had been "strong words" between them on a number of occasions, but said Mr Lenihan had "always been courteous".
Former Education minister Mary Hanafin spoke of his "astonishing courage" in the Department of Finance. Despite his illness, "he never missed a meeting,” she said.
They had been friends going back a very long way, their parents had been friends, they had socialised together and attended each other’s weddings.
She said she had encouraged him to take a rest on many occasions, but he had replied that he was fine and that his doctors had told him that hard work was the way to beat the illness.
Pat Farrell, a former general secretary of Fianna Fail, said he had had a long chat with Mr Lenihan a few weeks ago.
"On the day, I was taken aback. It was clear that his illness had taken a toll on him physically. But he was still optimistic. He said if he didn't defeat it, it would defeat him."
Tanaiste Eamon Gilmore described Brian Lenihan as "a really lovely man. He fought his illness so valiantly, and worked so hard. Everybody in Leinster House had warm feelings for him".
Social Protection minister Joan Burton, said she has first met Brian Lenihan 20 years ago when he was helping his father in the 1990 presidential election and she was helping to run Mary Robinson’s campaign in Dublin West.
He was "engaged, charming and clever," she recalled. Asked about his political legacy, she said he would be remembered as "far more than the bank bailout and the bank guarantee".
Part of his problem was that he had to cope with the big economic decisions on his own. "He and I often talked about how little advice there was in Ireland for the kind of crisis that the country was facing," she said. "I remember urging him to get people with international banking experience to be available to give advice. He laboured under a great burden there, on his own."
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