David Cameron's father Ian died today after suffering a stroke while on holiday in France.
Downing Street said the 77-year-old died shortly after the Prime Minister reached the hospital in the south of the country.
"It is with deep regret that we can confirm Ian Cameron died earlier this afternoon," the spokesman said.
"He passed away shortly after the PM arrived at the hospital in France where he was receiving treatment."
The Prime Minister's spokesman said Ian Cameron's death was not believed to be connected to any previously-existing medical condition.
He and the premier's mother Mary were halfway through a two-week holiday when he suffered a stroke and heart complications overnight.
He was taken to a hospital near Toulon, where Mr Cameron rushed to see him after being informed of the situation at around 6am this morning.
The premier was accompanied by brother Alex and sister Clare on the commercial flight from London's City airport.
Downing Street said Ian Cameron was not thought to have met the PM's new daughter, Florence, who was born last month.
Number 10 said French President Nicolas Sarkozy had intervened to arrange a helicopter to rush Mr Cameron to the hospital so he could see his father.
The PM is expected to remain in France overnight, but his movements after that have not been decided, according to the spokesman.
Mr Cameron touched down in France at around 12.30pm, after missing Prime Minister's Questions to take a 9.30am flight.
Sources close to the PM said he was "incredibly grateful" that the French authorities had provided air transport. It is understood he would probably not have been able to reach his father in time otherwise.
Friends said Mr Cameron was "relieved" to have been at the bedside, and was "pleased" that his father died peacefully and during a "happy family holiday".
Ian Cameron was said to have been "proud" to see his son become Prime Minister, and had visited both 10 Downing Street and Chequers. The family's holiday plans had prevented him meeting his new granddaughter before now.
Mr Cameron previously described his father as a "huge hero figure".
Ian Cameron was born with both legs deformed, and endured repeated operations in an attempt to straighten them and ease his pain.
However, despite his disability, he forged a successful career as a stockbroker.
In an ITV interview before the General Election, the Tory leader said: "My father is a huge hero figure for me.
"He's an amazingly brave man because he was born with no heels - quite a disability. But the glass with him was half-full, normally with something alcoholic. I think I got my sense of optimism from him."
Deputy Prime Minister Nick Clegg said: "My thoughts and condolences are with David and his family at this time.
"Despite the sadness of today, I am very glad that David's father lived to see him become Prime Minister and that David was able to be at his father's side at the end."