Former Tory foreign secretary Lord Pym has died at the age of 86 after a prolonged illness, his family has said.
Lord Pym often opposed the views of Margaret Thatcher
He served in the role during the 1982 Falklands War following the resignation of Lord Carrington.
But the then prime minister, Margaret Thatcher, removed him from the cabinet after her second election win in 1983.
Prime Minister Gordon Brown called him a man of "decency and principle". Tory leader David Cameron said he had been a politician of "great distinction".
Lord - then Francis - Pym was seen as a leading "wet" within the early Thatcher cabinet, arguing against some of the economic reforms advocated by the prime minister and her allies.
In the run-up to the 1983 election, he cautioned against a landslide victory for his party, which later happened.
Lord Pym was sacked during the following reshuffle and was made a peer four years later.
Educated at Eton and Cambridge, he first entered the Commons in 1961 as MP for Cambridgeshire after a career in business.
He was awarded the Military Cross and twice mentioned in despatches after serving as a captain in the 9th Royal Lancers during the African and Italian campaigns of World War II.
During his long career, Lord Pym was also Northern Ireland secretary and defence secretary, also serving in the cabinet of Edward Heath.
Mr Brown said: "I was saddened to hear of the death of Francis Pym, and my thoughts are with his family."
He added: "He was a man of great decency and principle and everyone will remember him as a good man who always did what he thought was right."
Mr Cameron said: "I was sad to hear of the death of Lord Pym. He served the country he loved with great courage in wartime and great distinction in peace. His was a life dedicated to the cause of public service."
In a statement, Sir John Major, prime minister from 1990 to 1997, said: "When I entered politics as a young candidate, Francis Pym was my neighbour, mentor and friend.
"He served his country in an exemplary fashion, in war and peace, in the Commons and the Lords."
Sir John added: "Francis Pym leaves a political legacy of great achievement, and - for me personally - a legacy of lasting friendship."
Jim Prior, a fellow member of the Thatcher cabinet, said: "He was a very good, decent man, who really was a major part of the Conservative Party in the 60s and 70s. He was perhaps disappointed at the end that he didn't achieve more."
Former Conservative chairman Lord Patten told BBC News 24: "He thought of himself primarily as a public servant, as a patriot, and secondly as a Conservative politician and minister.
"And I think that is the right way round for people to see things in politics. Country comes before party.
"I think he exemplified a certain tradition of public service in politics which we would be the poorer without. He was a lovely man."
A private family funeral will take place soon and a memorial service will be held later in the spring.