Baroness Thatcher served as prime minister between 1979 and 1990

A selection of some of these, put together by the Press Association, are included here:

I am delighted to congratulate Margaret Thatcher on the achievement of her 80th birthday. We have reflected this year on how Winston Churchill's political will and iron courage saved a nation.

"What Churchill did in wartime, Margaret Thatcher did in peacetime. Her political will and her iron courage saw off the threats to our way of life that Britain faced in 1979.

"We all owe her an enormous debt. I wish her well for her birthday and for many years to come."

"Happily for all of us, Margaret's 11 years of triumph, which ended in tragedy, still stand as a period of astonishing achievement.

"No Government did more in the 20th century to change the shape of our world fundamentally and very largely for the better.

"The clash between Margaret and myself, which ended our partnership, will be remembered much less than the brilliance of her achievements. The real triumph was to have transformed not just one party but two, so that when Labour did eventually return, the great bulk of Thatcherism was accepted as irreversible."

"I will never forget my first sight of Margaret Thatcher. It was in 1965. I was attending the Conservative conference in Blackpool as a party worker.

"Margaret was replying to a debate on taxation. I had heard of her, but I had never seen her before. At the end of the debate, this very good-looking blonde woman, wearing a beautifully-tailored suit and a very impressive hat stood up to address the conference.

"She looked as if she was on her way to a very smart wedding. She spoke with huge authority and enthusiasm on what could have been a very dry subject and she took the conference by storm.

"Ten years later, when she became the leader of the Conservative Party, the late James Callaghan was quoted as saying 'we have just won the next election'. He could not believe that a woman leader of the Conservative Party would beat him. Had he been at the Conservative conference in 1965, he would not have made that patronising remark.

"He was neither the first nor the last person to underestimate this remarkable woman."

"Mrs Thatcher said what she meant and meant what she said. And did it. Although I thought the policies were catastrophic in terms of democracy, she did not do anything by deception.

"Everyone knew what she wanted to do."

"Margaret Thatcher's untruths in relation to the Peruvian peace proposals in the Falklands War and the Solicitor General's letter in the Westland Helicopter affair pale into insignificance compared to the lies that Blair has told us in relation to the Iraq war."

"She has my warmest congratulations on reaching such a splendid anniversary. I would wish to say to her: `Why don't you come back? Remember that Gladstone formed his fourth administration when he was 83'.

"There is such goodwill towards her in Parliament that there would be no difficulty in passing the legislation to return her to the Commons. On the other hand, she might well yet make more history and remain as Prime Minister in the House of Lords."

"The greatest tribute people pay these days is 'Come back Maggie'."

Lord Gilmour, who was also sacked by her as Lord Privy Seal, said: "I hope she has a very happy birthday."

Lord Tebbit said: "I would just like to wish her many more happy birthdays and good health."

"I served Margaret Thatcher as chief whip between 1963 and 1987, as well as in many other positions. She was for me a wonderful boss, always ready to listen to well-put-together arguments and a reasoned case.

"I don't think I ever went to a meeting where she was not as well informed as any of her colleagues."

"I wish her many happy returns and hope she has a good year ahead of her."

"She braved an awful period in opposition as all Tory leaders do and no one thought a woman could ever win an election. She did and was one of the great prime ministers of the last century.

" I have always liked her as a person, but regrettably I don't see her very much these days."

"I would wish her a happy birthday, certainly."

"It was very exciting and a privilege to be a member of her government and to have a relationship with her that went back to 1955, when I took her place as the Conservative candidate for Dartford.

"I wish her every happiness in the years ahead."

"I wish Lady Thatcher a very happy 80th birthday.