"We must be the happiest family in Britain," Gordon Brown said

The child, weighing 8lb 1oz, was born by Caesarean section on Friday morning and both mother and baby are said to be "fine".

Speaking outside the Edinburgh Royal Infirmary, Mr Brown said everything had gone well with the birth and revealed that the couple had named their son John, after the chancellor's own father.

News of Mrs Brown's pregnancy appeared in March - just over a year after the couple's first child, Jennifer Jane, died when she was only 10 days old.

"It was great and everything went well, Sarah's extremely fit, she really did extremely well and therefore we feel we must be the happiest family in Britain," Mr Brown said.

"We've had a difficult two years but we've been heartened by all the good wishes that everyone has given us and all the support we've had from this hospital.

Our baby is wonderful, he's beautiful, he's really full of energy and I think he's going to keep me awake for quite a number of days, weeks and months Gordon Brown Watch Gordon Brown

"When we came in yesterday morning we drove across the Forth Bridge, saw the rail bridge at the side at about 6.30 yesterday morning, and we just felt it was all going well and it did go well and we're extremely happy.

"John is quite a well known name for the Browns and it's a pretty well known name in our family, but there will be a middle name to distinguish the baby from the many other John Browns there are."

The chancellor added that he was looking forward to learning his nappy changing duties and that John was a strong boy who was "wonderful, beautiful and really full of energy".

'Gorgeous baby'

He said he planned to take a period of paternity leave and that the couple hoped to get home on Tuesday.

GORDON BROWN Born 20/02/51 in Glasgow 1983 becomes MP for Dunfermline East 1987 joins Labour's frontbench 1992 shadow chancellor Blair appoints him chancellor after 1997 Labour victory Marries PR executive Sarah Macaulay in 2000 Full profile

Mrs Brown's mother, Pauline, said Sarah and the baby were "both doing fine" as she left the hospital with her husband, Patrick Vaughan.

Dr Rhona Hughes, consultant obstetrician at the hospital, said: "Sarah and Gordon are both delighted - it was a very emotional moment and they both wept tears of joy."

Prime Minister Tony Blair was one of the first to offer Mr and Mrs Brown his congratulations.

"This is wonderful news. Cherie and I are absolutely delighted," he said.

Tory leader Iain Duncan Smith said he was "overjoyed".

John Brown, the new baby's uncle, said the parents were "in awe"

"Children are an immense blessing and I am sure their new son will bring great fulfilment to their lives," he said.

Both the chancellor and his wife have expressed their thanks to the staff at the hospital.

Harry Potter author JK Rowling, who has a home in Edinburgh, visited the Browns in hospital on Friday evening.

On leaving, she said the baby was "really, really gorgeous" and the couple were both well.

Mr Brown's elder brother John said: "The whole family are delighted at the birth of Sarah and Gordon's baby. He is a beautiful boy."

First child lost

The Browns' first child, Jennifer Jane Brown, was born in December 2001 at Forth Park Hospital in Fife seven weeks premature.

The Browns called their first child an "inspiration"

She died at the Royal Infirmary in Edinburgh a little more than a week later after suffering a brain haemorrhage.

At the time, Mr Brown, 52, said she had been an "inspiration" to both him and his wife, whose lives would not be the same again.

The chancellor and his wife, 38, who works under her maiden name of Sarah Macaulay, were married in August 2000 at a private ceremony in North Queensferry, Fife.

Ministerial births in Downing Street have become more commonplace, with Tony Blair in 2000 becoming the first prime minister in 150 years to father a child while in office.