Gordon Brown and David Cameron have clashed in the Commons over the reasons for Barack Obama's US election victory.
The Conservative leader said the change offered by Mr Obama contrasted with Labour's offer of "more of the same".
The prime minister said Mr Obama had triumphed because he was a "serious man for serious times" and embodied "progressive" values shared by Labour.
Earlier both men and Lib Dem leader Nick Clegg had united in praise of the Democrat Mr Obama's victory.
The BBC's political editor Nick Robinson said both Labour and the Conservatives wanted to associate themselves with the factors behind Mr Obama's success and absorb some of the political magic he displayed on the campaign trail.
In the Commons, Mr Brown said he hoped to talk to Mr Obama "very soon", saying his election was of "historical significance".
But Mr Cameron taunted him with a line the PM used in his Labour conference speech, saying: "I read this morning that you had sent a message to the President-elect. Presumably it wasn't: 'This is no time for a novice".'
After Mr Obama's victory, which he said had restored America's status as a "beacon of hope", Mr Cameron said British voters were now entitled to know "how much longer they have to put up with more of the same from this government that's failed".
Mr Brown said the Conservatives had opposed all the policies to support the troubled US economy that Mr Obama had endorsed and added the "only change they represent is that they change their minds every week".
In electing Barack Obama, America has made history and proved to the world that it is a nation eager for change
Lib Dem leader Nick Clegg challenged Mr Brown to follow Mr Obama's pledge to cut taxes for those on low and middle incomes, adding that he had failed to "learn" from the senator's popularity.
Earlier, the leaders of Britain's three main political parties had all praised Barack Obama's victory in the US presidential election. Mr Brown and Mr Cameron also paid tribute to the Republican candidate, senator John McCain.
The prime minister, who met Mr Obama in London during the summer, said he was a "true friend of Britain" who shared "many values" with the him.
"We both have determination to show that government can act to help people fairly through these difficult times facing the global economy."
He said the election was "a moment that will live in history as long as history books are written".
Mr Cameron said the US presidential race had been an "inspirational contest" and Mr Obama's victory meant people across the world would see the US "for what I believe she is - a beacon of opportunity, freedom and democracy".
Offering his "wholehearted congratulations" he added: "In electing Barack Obama, America has made history and proved to the world that it is a nation eager for change."
This was a victory for optimism over pessimism, for hope over fear
Mr Clegg said Mr Obama must take a "radical new approach" on climate change, the economy and international security issues, adding: "The weight of people's hopes and expectations on Barack Obama is immense."
Later International Development Secretary Douglas Alexander told the BBC the "statesmanlike words" at the start of the day, and later clash over the reasons for his victory was a "very British welcome".
He said politicians would be trying to interpret the results - which he saw as a "huge victory for progressive politics".
Foreign Secretary David Miliband and his Tory counterpart William Hague were also at odds over what parallels could be drawn from Mr Obama's victory.
Mr Miliband agreed governments that offered only the "status quo" would not be re-elected but said Labour had renewed itself under Gordon Brown - most recently in the way he had dealt with the economic crisis.
"I don't think Gordon Brown is John McCain and I certainly don't think that David Cameron is Barack Obama," he said.
David Cameron reacts to Obama's win
Mr Hague however said there had been "great personal chemistry" between Mr Obama and Mr Cameron at a meeting in July.
He said while they were at "different positions on the political spectrum", Tony Blair and George Bush and John F Kennedy and Harold MacMillan had worked together "at the height of Anglo-American co-operation".
"I believe that could happen under David Cameron and Barack Obama," he said.
Scotland's First Minister Alex Salmond sent a message to Mr Obama offering his "heartfelt congratulations" on a "wonderful and historic" election victory.
"It ushers in a new era of hope for the United States and its role in the world. This was a victory for optimism over pessimism, for hope over fear," he said.
First Minister for Wales Rhodri Morgan said it was a "stunning victory" and that Mr Obama now had two months to prepare for the "huge job of translating that hope into improved conditions for jobs and health domestically for America".
Northern Ireland's First Minister Peter Robinson and Deputy First Minister Martin McGuinness also congratulated the president-elect.
Mr Robinson said Mr Obama's success was an historic event. Mr McGuinness said he looked forward to "developing and deepening our economic and cultural interests with the US" and offered his "sincerest congratulations".
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