Blair to leave office on June 27

Prime Minister Tony Blair said on Thursday he will quit on June 27, 10 years after winning power in what was hailed as a new dawn for Britain that has since been darkened by the Iraq war.

Blair's resignation triggers a contest for the leadership of the ruling Labour Party, which finance minister Gordon Brown is favourite to win. Brown would then become prime minister.

"I've been prime minister of this country for just over 10 years," Blair told party members in Trimdon in his northern England constituency.

"I think that's long enough, not only for me, but also for the country and sometimes the only way you conquer the pull of power is to set it down."

Blair defended his record in office, saying "I did what I thought was right" during his decade in power.

Tough choices

Blair said Britain had changed for the better since he took over as prime minister in 1997.

But there were difficult decisions along the way, particularly when there was widespread opposition, leading to his fiercely-held conviction to be misinterpreted as "messianic zeal", he added.

"Doubt, hesitation, reflection, consideration, reconsideration — these are all the good companions of proper decision-making but the ultimate obligation is to decide," he said.

Blair said some decisions, such as the independence Labour granted to Britain's central bank, the Bank of England, to set interest rates, were accepted "quite quickly".

But others were harder to make and sometimes, the "completely unexpected" led to isolation, such as his decision to stand "shoulder to shoulder" with Washington after "9/11", he told the audience of Labour supporters.

"Removing Saddam (Hussein) and his sons from power, as with removing the Taliban, was over with relative ease.

"But the blowback since from global terrorism and those elements that support it has been fierce, unrelenting and costly.

"For many it simply isn't and can't be worth it. I think we must see it through... It's a test of will and of belief and we can't fail it."

Despite what he said were the "duller tones" of reality compared to the "rainbow" hues of political vision, Blair said it had been an honour to serve as Labour leader since 1994 and prime minister since 1997.

Whatever people's perceptions of his time in office, he said: "I ask you to accept one thing, hand on heart, I did what I thought was right.

"I may have been wrong. That's your call but believe one thing if nothing else, I did what I thought was right for our country."

Domestic troubles

Blair, U.S. President George W. Bush's closest ally over Iraq, leaves office out of favour among voters for sending British forces to join the 2003 U.S.-led invasion.

A Labour Party rebellion in September forced him to say he would quit within a year to allow Brown, his long-time heir apparent, to take over.

But Blair will also be remembered for helping bring peace to Northern Ireland after decades of violence, winning three straight elections for Labour for the first time and dragging it from its left-wing roots to the centre of British politics.

An opinion poll published by the Guardian newspaper on Thursday showed 60 percent of voters believed Blair would be remembered as a force for change, though not always good. The ICM poll said 44 percent believed he had been good for Britain.

Blair had long been expected to hand over power before the end of his third term to let another Labour leader guide the party into the next national elections, expected in 2009.

Brown, whose official residence is next door to Blair's in London's Downing Street, has waited with increasing impatience for the departure of his neighbour. Critics say their rivalry, often bitter, has diluted the government's effectiveness.

Blair quits as only the second prime minister in a century to have served 10 years, tainted by a corruption scandal in which he became the first serving prime minister to be quizzed by police in a criminal probe.

Brown's chief challenge will be to revive support for Labour and overtake the opposition Conservatives in the opinion polls.

Conservative leader David Cameron, 40, has revitalised the party of Margaret Thatcher — the only prime minister to hold power longer than Blair in the past century — since he became leader in 2005. Polls suggest he could win a slim majority in parliament in national elections.