Sky Television, citing senior Labour Party members, later said Mr Blair will step down from office on May 4, 2007.
A junior minister and seven official aides have resigned demanding that Mr Blair quit, a day after it was revealed that 17 Labour MPs signed a letter calling for the prime minister to step down.
Tom Watson, a junior defence minister was the highest ranking MP to quit on Wednesday and said it was not "in the interest of either the party or the country" for Mr Blair to stay in office.
"I share the view of the overwhelming majority of the party and the country that the only way the party and government can renew itself in office is urgently to renew its leadership," he wrote.
In addition six parliamentary private secretaries members of parliament who act as unpaid ministerial aides, also announced they were quitting in protest at the current limbo.
The private secretaries on the lowest rung of the government ladder and aren’t high profile members of parliament.
Mr Blair, in a letter to Watson, warned that disunity could only harm Labour, which spent 18 years in opposition prior to 1997.
"To put all this at risk in this way is simply not a sensible, mature or intelligent way of conducting ourselves if we want to remain a governing party," he said.
Announcement speculation
Speculation continues to intensify over Mr Blair's future following a newspaper report that he will resign next July.
Reports have also emerged from the BBC and Britain's domestic Press Association (PA) that the British Prime Minister will make his intention to resign in a year public on Thursday, confirming comments from key allies.
The prime minister is due to visit a school in London with the Education Secretary Alan Johnson, and PA reported that Mr Blair would use a pre-planned photo opportunity with Mr Johnson to outline his plans.
Mr Blair reportedly feels he has to give clarity to his governing Labour Party and the country over his intentions, PA said, citing senior sources in Downing Street.
But a spokesman for the embattled premier said: "I am not aware of the prime minister having any plans to do that."
The new developments for some recalling the way Margaret Thatcher was brought down by her Conservative Party in 1990 came hours after The Sun newspaper reported that Mr Blair plans to stand down as premier in July.
In Britain, governing political parties can replace their leader without referring the matter to the country in an election. This happened when John Major replaced Ms Thatcher as Conservative prime minister.
The paper said he would resign as leader of the Labour Party on May 31, triggering an eight-week internal party election that his long-serving finance minister Gordon Brown is likely to win.
Leaked memo
The report came a day after the publication of a leaked memo detailing an "exit strategy" for the 53-year-old British leader, who would mark 10 years in office next May.
Mr Blair's office refused to comment on the front-page report by The Sun, whose backing of Blair was widely seen as instrumental in his landslide 1997 general election victory.
Other newspapers meanwhile said that Labour MPs want Blair to confirm remarks from his environment secretary, David Miliband, on Tuesday that the "conventional wisdom" was that he can be expected to stand down in 12 months.
The Guardian daily reported that Gordon Brown, the Chancellor of the Exchequer, has demanded the prime minister set a timetable for his resignation and make it public.