A new little Blairite is on the way, Cherie tells Tony

Tony Blair and his wife, Cherie, shocked their friends and surprised the nation last night by announcing that they are to have a baby in May.

Tony Blair and his wife, Cherie, shocked their friends and surprised the nation last night by announcing that they are to have a baby in May.

Cherie's news that she is expecting a baby - her fourth - was greeted by delighted congratulations from the Prime Minister's cabinet colleagues and his political opponents.

The baby, which is thought to have been conceived during the family's summer holiday near Pisa in Italy, will be the first born to a serving Prime Minister this century and is certain to raise questions about Mr Blair's long-term readiness to use Downing Street for the family home.

Confirming the news before it was leaked in a newspaper, a Downing Street spokesman said: "The Prime Minister and Mrs Blair had hoped to announce this later in the pregnancy as only a small number of family and friends and No 10 officials are aware.

"They are delighted at the news, which came as a total shock. The baby is expected in May." He added: "They are sorry they have not been able to tell all their friends before it has become public in this way."

The birth of a child is likely to highlight the Government's policies for children in the spring Budget, which the Chancellor has indicated will include more measures to support families.

The Prime Minister's May baby - the third anniversary of his winning power to Downing Street - may complicate Mr Blair's plans to go for early election in the following spring, when the baby is a year old.

But it will reinforce Mr Blair's commitment to the family - raised in his maiden speech to the Commons - with impeccable timing in the run-up to the general election.

Mo Mowlam, the Cabinet Office Minister, when told of the pregnancy, said: "How wonderful." In Scotland, Donald Dewar, the First Minister, said: "I am delighted to hear the news" And Gordon Brown, the Chancellor, said: "I am really pleased for the whole family. It is wonderful news."

John Burton, Mr Blair's constituency agent in Sedgefield, said: "The whole constituency will be thrilled. The first thing my wife said when she found out was that it explained why Cherie looked under the weather when we saw her last."

Charles Kennedy, the leader of the Liberal Party, said: "Great news. My warmest personal congratulations and good wishes to both Tony and Cherie. I'm sure everyone will be delighted for them. And from the Tories, William and Ffion Hague said: "It is wonderful news. Congratulations to Cherie and Tony. We are delighted for the whole family."

Mr Blair has repeatedly emphasised his wish to provide a normal family upbringing for his three children - Euan, 15, Nicholas, 14 and Kathryn, 11 - in spite of living "above the shop" at Downing Street.

But Mr Blair, 46, and Cherie, 45, may not wish to stop at four children. In July, he told Siobhan Maher, 13, who had won a competition to interview him for BBC1's Newsround: "We would have had five if, well, if we had carried on, I suppose." When Siobhan, of Solihull, West Midlands, said she was one of five, Mr Blair said: "I think big families are great."

However, the new baby could cause a space crisis in Downing Street. The Blairs have already swapped accommodation with Mr Brown at next door at No 11 because the bachelor flat at the top of No 10 was not big enough for their family.

The last time a Prime Minister became a father while in office was in 1848 when the wife of Lord John Russell, aged 56, gave birth to a boy.The Blair are the only Downing Street occupants this century to have a child while in office.

To protect their children's privacy, the Blairs took the unprecedented step of seeking a Press Complaints Commission judgement after a row about their choice of school for Kathryn.