In a firm slap-down to MPs such as Robin Cook, the party's foreign affairs spokesman, who earlier this week predicted a "landslide" victory for Labour at the general election, Mr Blair said he was taking nothing for granted.
Mr Blair told Labour's Scottish conference in Inverness that last week's by-election in Wirral South was a historic win for Labour.
But he stressed: "A by-election is still a by-election. A general election is still to come, and there is only one opinion poll that matters and that is the one on election day.
"I am and remain the eternal warrior against complacency. We are doing well but we take nothing for granted," he said.
Mr Blair's words will also be seen as a warning for his party not to get carried away by opinion polls such as the Gallup Poll yesterday in the Daily Telegraph which put the Tories an unprecedented 26 points behind Labour with less than two months to go to polling day.
Mr Blair said: "From now until the day of decision comes, we carry on as we have been doing, patiently, sensibly, building up trust with the British people with responsibility and humility.
"Even if we win, there will be no victory dances. For then, the hard work in serving our country begins in earnest."
Addressing Labour's last major political event in Scotland before the election, Mr Blair renewed his pledge that if his party won the general election a Labour government would legislate in its first year for a Scottish Parliament.
"We will hold a referendum as soon as possible after coming to office. I will be here campaigning for a 'yes' vote in that referendum. There will be two questions. I will be campaigning for two 'yes' answers," he said.
Labour plans to ask the Scottish people two questions in a plebiscite - first whether they want a Scottish Parliament and second whether it should have tax-raising powers.
Earlier yesterday Alex Salmond, the Scottish National Party leader renewed his call for such a referendum to include his favoured option of full-blown independence.
But Mr Blair rounded on the SNP, accusing them of sitting on the fence for failing to say whether they would support a 'yes' campaign.
Mr Blair also announced plans to free up an extra pounds 30m for patient care in Scotland.
He said George Robertson, Labour's spokesman on Scottish affairs, had come up with a plan to cut the number of NHS trusts in Scotland from 45 to 25.
"With our other savings it will mean pounds 30m more for patient care in Scotland," he said.
Mr Blair also renewed his pledge to end the "scandal" of hereditary peers.Reuse content