Cecil Parkinson has died aged 84 after what his family said was “a long battle with cancer”.
As Conservative Party chairman under Margaret Thatcher in the early 1980s, he played a key role in the Tories’ 1983 general election victory.
Lord Parkinson quit the cabinet soon after when it emerged his ex-secretary Sara Keays was carrying his child.
Prime Minister David Cameron said he was “a man of huge ability” who had helped transform the UK in the 1980s.
Paying tribute in Downing Street, Mr Cameron said he had “learnt a lot” from Lord Parkinson at the start of his political career, describing him as part of “a great political generation that really did extraordinary things for our country”.
As they confirmed his death, a family spokesman said: “We shall miss him enormously. As a family, we should like to pay tribute to him as a beloved husband to Ann and brother to Norma, and a supportive and loving father to Mary, Emma and Joanna and grandfather to their children.
“We also salute his extraordinary commitment to British public life as a member of parliament, cabinet minister and peer – together with a distinguished career in business.”
The BBC’s assistant political editor Norman Smith said Cecil Parkinson was one of Margaret Thatcher’s closest political allies but said that his career was “undone” by the scandal that engulfed him following his affair with Ms Keays.
The former chartered accountant and businessman was central to Margaret Thatcher’s political agenda and achievements in office, he added.
Lord Parkinson was in the front rank of Conservative politics for three decades, first being elected to Parliament in 1970.
After becoming a junior minister after Margaret Thatcher’s 1979 election victory, he swiftly rose through the ranks and was named party chairman and elevated to the cabinet in 1981. He was a member of the war cabinet during the 1982 Falklands conflict.
He was tipped to be named foreign secretary after overseeing the Tories’ landslide election victory in 1983. But he was given the more junior role of trade and industry secretary and it later emerged he had fathered a child with his former secretary, prompting him to resign in October 1983.
Former Conservative cabinet minister Michael Portillo said this scandal had “definitely held back his career” but the fact that he was offered a cabinet post at all was testament to his closeness to the PM.
Former foreign secretary Malcolm Rifkind said Lord Parkinson would have been “the most natural candidate” to succeed Margaret Thatcher had events not turned out in the way they did.
“John Major eventually filled the gap that Cecil Parkinson would have had,” he told the BBC News Channel. “But Cecil Parkinson was in reality a Thatcherite while John Major, as Margaret Thatcher eventually discovered, was not nearly as close to her, as she had hoped and assumed”.
The former prime minister regarded Cecil Parkinson as “one of us”, Mr Rifkind added: “He shared her views, thoughts and ideas. She was comfortable with him and had confidence in him, In addition, at a personal level, he was able to charm her.”
After being brought back into government in 1987, Cecil Parkinson served as energy and transport secretaries.
Lord Parkinson stood down as an MP in 1992 and was elevated to the House of Lords. He briefly made a comeback as Tory Party chairman, under William Hague, after the party’s general election hammering in 1997.
Lord Hague described him as “an exceptional talent and an extraordinarily nice man to work with”.
Current members of the government have also been paying tribute. Chancellor George Osborne tweeted: “Sad to hear of death of Cecil Parkinson. I worked with him when he was party chairman in 1997-8 – he was there in our hour of greatest need.”
And former minister Alan Duncan said Lord Parkinson was “personable, amusing, easy-going and mischievously witty”. “He started as Margaret Thatcher’s great marketing man for overseas trade and turned into one of the great personalities of the Thatcher era,” he said.
When the scandal over Cecil Parkinson’s infidelity broke during the 1983 Conservative Party conference, Ms Keays claimed the politician had agreed to leave his wife Ann for her.
In her book, A Question Of Judgment, Ms Keays claimed that Mr Parkinson had “begged” her to have an abortion and that he had “haggled over every pound” of financial support for their daughter Flora.
But Mr Parkinson himself insisted that he had voluntarily made more than adequate provision for them.