The Labour Party was set up in 1900 to fight for representation for the Labour movement - trade unions and socialist societies - in Parliament.

The creation of a national government during the First World War gave the party its first ministers and a taste of political power.

After the war, the decline of the Liberal Party saw Labour becoming the main opposition party, but although twice in power, Labour governments were short lived. It was the Second World War that changed the party's fortunes.

A coalition government took over in 1940 and the Labour leader Clement Attlee became deputy to Winston Churchill. The Beveridge Report, prepared during the war years, created the vision of a better society, and heralded the social changes that would follow in peacetime.

A Labour landslide at the 1945 election saw massive post-war changes for the UK. Post-war Britain saw the creation of the welfare state and the nationalisation of key industries like coal, steel and the railways. But disappointment followed; the Tories won the 1951 election, and an era of prosperity helped to keep Labour out of power for 13 years.

In the 1960s, under the leadership of Harold Wilson, the Labour Party clawed its way back to power, first with a tiny majority in 1964, and then a convincing victory in 1966. But the new administration was hit by economic problems and after the pound was devalued in 1970, the Conservatives returned to power.

By 1974 Labour was back, winning two elections in the same year, but facing new problems. After the surprise resignation of Harold Wilson as party leader, Jim Callaghan became prime minister. He quickly found himself presiding over an economic crisis, requiring a hefty international loan and cuts in public spending.

At the 1979 election, Labour was voted out and Margaret Thatcher moved into Downing Street. It marked the start of 18 years in opposition for Labour, and one of the bleakest periods in the party's history.

Key players

The Conservatives were to win four elections in a row, three under Mrs Thatcher and another under John Major. During Labour's wilderness years, the party leadership passed first to the left-winger Michael Foot followed by Neil Kinnock and then John Smith, who was seen as the prime minister in waiting. His sudden death in 1994, after a heart attack, was a shattering blow for the party.

In the contest that followed, Tony Blair was elected leader and the progress of modernisation begun by Neil Kinnock continued with a vengeance. The architects of "New Labour" were pitted against the forces of tradition, with their attachment to socialism - regarded by the leadership as an electoral liability.

In a symbolic break with the past, the Clause 4 commitment to nationalisation was torn up.

Re-positioned as a party of the centre-left, Labour approached the 1997 election at a time when the Conservative government appeared to be running out of ideas. Individual Tory MPs were also tainted by allegations of "sleaze".

Labour's election manifesto presented the party as one offering a "new politics" that would mean an end to old divisions between Left and Right. The result was a landslide victory that made Tony Blair Prime Minister.

Old "tax and spend" policies were out. The unions would be treated fairly but without any favours. And Labour would welcome business as a partner. In government, the party clearly intended to hold the middle ground.

The ambition was to be the first Labour government to win a second full term. But after the honeymoon, rows began to surface within the government. Embittered party members spoke out over the "control freak" tendencies at the top of the party, and the penalties for being "off message". The activities of spin doctors at the heart of government also led to resentment.

Leading members of the Labour administration found themselves in the headlines for all the wrong reasons. The Paymaster General, Geoffrey Robinson, was criticised for not declaring an offshore trust. The Welsh Secretary, Ron Davies, resigned after a "moment of madness" on Clapham Common.

Peter Mandelson, one of those credited with re-inventing the Labour Party, resigned not once but twice. He first left the government in 1998, when he was Trade Secretary, after a row about a home loan. He also quit as Northern Ireland Secretary following allegations over his role in getting passports for the wealthy businessmen the Hinduja brothers.

The party has been beset by widespread opposition over the war in Iraq, tuition fees and the war on terror but has always managed to bounce back.