Mr Brown's defence of the prime minister's achievements in the NHS and on the international stage come after he praised Mr Blair at this morning's Cabinet meeting.
"I think I spoke for millions of people when I said to the Cabinet today that Tony Blair's achievements are unique, unprecedented and enduring," Mr Brown said this afternoon.
A No 10 spokesperson said that as the meeting ended and Mr Blair prepared to leave, the chancellor thanked him for the "unique leadership" he had given his party, Britain and the world.
And in Washington, US president George Bush said he would "miss" his friend once Mr Blair left office, quoting an old Texan saying that whatever the prime minister told you, "you could take to the bank".
But opposition politicians have been less glowing in their evaluation of the prime minister's decade in power, with Conservative leader David Cameron saying in his personal blog that "a lot of people will look back on the last ten years of dashed hopes and big disappointments, of so much promised so little delivered".
Shadow foreign secretary William Hague, comprehensively defeated in 2001's general election by Mr Blair, grudgingly conceded that the prime minister had been a "formidable opponent", and "really the most dangerous opponent the Conservative party has ever had".
"That is partly because of his ability to persuade people that he is really, secretly, a Conservative, even though he is leader of the Labour party," Mr Hague added.
Liberal Democrat leader Menzies Campbell meanwhile condemned the "missed opportunities" of the prime minister's legacy.
Mr Campbell said Mr Blair would be "rightly remembered" for becoming the first Labour prime minister to win three consecutive general elections, yet concluded that his overall period in office had "shattered" Britons' hopes for a "new kind of politics".
Mr Blair told Labour party activists at his Sedgefield constituency today that he would draw a close to his ten years at No 10 on June 27th.
"I've come here where my political journey began and where it is fitting it should end," he said in a highly-charged address.
"I may have been wrong," Mr Blair continued. "That's your call. But believe one thing if nothing else; I did what I thought was right for the country."
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