A post-mortem examination has found former Foreign Secretary Robin Cook died of hypertensive heart disease.
Mr Cook resigned from the Cabinet over the Iraq War
The MP for Livingston collapsed and fell while hillwalking in Sutherland at the weekend.
The examination confirmed that he died from his illness rather than injuries sustained in the fall.
Mr Cook's funeral will be held at St Giles Cathedral in Edinburgh on Friday morning. Prime Minister Tony Blair is on holiday and will not attend.
The eulogy at Friday's funeral will be delivered by Chancellor Gordon Brown.
Former US Secretary of State Madeleine Albright is also expected to attend.
Mr Cook, 59, was pronounced dead after being airlifted to hospital on Saturday.
He fell 8ft down a ridge near the summit of the 2,365ft Ben Stack in Sutherland.
The post-mortem examination was conducted at the Raigmore Hospital in Inverness.
Downing Street said Mr Blair was not expected to break off from his holiday for the funeral at 1100 BST and his deputy, John Prescott, will attend.
The prime minister may attend a memorial service later this year.
Mr Blair had paid tribute to Mr Cook, calling him an "outstanding, extraordinary talent".
Foreign Secretary Jack Straw described him as "the greatest parliamentarian of his generation".
Channel 4 racing pundit John McCririck accused the prime minister of snubbing the family and the memory of Mr Cook by not attending his funeral.
Mr Cook had been with his wife Gaynor when he collapsed
Mr Cook had resigned from Mr Blair's Cabinet in 2003 over the Iraq War.
Mr McCririck, a friend of horseracing fan Mr Cook for 20 years, will be among those speaking at the funeral service.
He said: "Robin's criticism of government policy was dignified, and never became personal or vindictive.
"If Margaret Thatcher can bring herself to attend Ted Heath's service, then surely Mr Blair ought, at least publicly, to show respect and gratitude to Robin."
A Crown Office statement said: "The procurator fiscal for Tain and Dornoch can confirm that a post-mortem examination following the death of Robin Cook MP has established the cause of death as hypertensive heart disease.
"Next of kin has been informed of the cause of death, and a death certificate has now been issued."