|Search ON THIS DAY by date|
In the second round of voting by party MPs Mr Foot defeated his main rival Denis Healey by 139 votes to 129 - an unexpectedly large margin.
The result has surprised political commentators who had predicted Mr Healey would win.
Mr Healey, who served as chancellor in James Callaghan's government until its defeat last year, had won the first round easily, with 112 votes to Mr Foot's 83.
It is believed MPs switched their vote from Mr Healey because Mr Foot's popularity as an MP, even among his opponents, is considered most likely to unite the party.
Deep divisions between the left and right of the party emerged last month at the party conference.
After the result was announced, Mr Healey commented, "Naturally, I am disappointed."
He has pledged to stand for deputy leader, and is also expected to take the position of shadow spokesman on foreign affairs.
The leadership contest was called after the former Prime Minister James Callaghan announced he was stepping down from the leadership three weeks ago.
Mr Foot's appointment has dismayed many on the right of the party.
Three of Labour's most prominent figures - former government ministers David Owen, William Rogers and Shirley Williams - have already said they cannot remain in a party that championed Mr Foot's main policies.
However, Mr Foot, at 67 the father-figure of the Labour left, declared in his acceptance speech that he would not compromise his left-leaning views.
He told journalists, "I am as strong in my socialist convictions as I have ever been."
He said he considered the two most important issues facing him to be nuclear disarmament and unemployment.
Mr Foot plans to lead the protest march against high unemployment planned for 29 November on Merseyside.
He also challenged the Conservative leader and Prime Minister, Margaret Thatcher, to hold an election as soon as possible.
A former journalist, Mr Foot served as employment secretary and leader of the House of Commons until Labour lost the election last year.
He is highly popular on all political sides in Westminster, and is known for his intellect and his witty speaking style.
He has run for the leadership before, losing in 1975 to Mr Callaghan, who went on to become prime minister.
The election of Michael Foot was one of the main factors leading to the start of three-party politics in Britain.
The following year, senior Labour figure Roy Jenkins joined the "Gang of Three" to defect from the party, forming the centre-left Social Democratic Party.
The party merged with the Liberal Party in 1988. It is now known as the Liberal Democrats and is the third-largest party in British politics after Labour and the Conservatives.
The split in the party as well as the Falklands War in 1982 and an ill-judged manifesto contributed to a heavy defeat for Labour in the general election of 1983.
Labour's share of the vote was just 27.6%, the lowest since 1918, and Michael Foot resigned the leadership.
He served the new Labour leader, Neil Kinnock, until 1992, and then retired from parliament.
The Labour Party remained in the political wilderness until Tony Blair took over the leadership and won the 1997 general election, ending 18 years of Conservative rule.
Michael Foot has written a number of highly-acclaimed books, including a two-volume biography of his political guru, prominent Labour left-winger Aneurin Bevan.
He celebrated his 90th birthday in 2003, and remains politically outspoken.
|Search ON THIS DAY by date|