Rhodri Morgan worked with Tony Blair in Labour's opposition days

Mr Morgan, who worked closely with the prime minister when Labour was in opposition, said Mr Blair's wife Cherie and older children could ask him: "Do you need to be putting yourself through this?"

But Mr Morgan said Mr Blair would also be under pressure to stay in office because of his experience at a time of global uncertainty.

Another leading Welsh politician, former Plaid Cymru leader Dafydd Wigley - who stepped down himself after heart problems - urged Mr Blair to share his duties with others to reduce his "presidential" role.

Tony Blair is one of the fittest people I know... nevertheless you have to look at the stress and strain that he has been under Rhodri Morgan

Mr Blair, 50, was said by his official spokesman on Monday to be "100% recovered" after hospital treatment for an irregular heartbeat.

Mr Morgan, 64, who has held Wales' top job since February 2000, told BBC Radio Wales that top politicians were "money rich but time poor".

He told the Good Morning Wales programme there was constant pressure on time and family life.

"Although Tony Blair is one of the fittest people I know - one of the fittest 50-year-olds I have ever come across... nevertheless you have to look at the stress and strain that he has been under over the past 12 months and I think everybody will think to themselves 'could it have anything to do with this?'."

Mr Morgan said: "I think probably it's worse for Cherie and even the children as they are getting to an age - apart from little Leo - where they are aware of what's going on and they may say 'Dad, or Tony, do you need to be putting yourself through this?'

Mr Blair is now back in Downing Street

'Learn lessons'

"But the problem is you look at the world - and I think Tony sees himself very much as a world statesman now - and you think 'who are there around?'.

"He's only 50 but on the other hand in length of time in a PM or equivalent position around the world there are very few people around now who've got his experience.

"And therefore the call to see what you can do to contribute to a safer world is going to be pressing very strongly on Tony Blair to stay right where he is because you need experienced hands on the helm during a period of international instability, as there undoubtedly is."

Mr Wigley, 60, announced he was giving up the presidency of Plaid Cymru three years ago when he underwent surgery for heart problems.

"I hope that Tony Blair, however ,does look at the way he works," said the former Caernarfon MP and assembly member.

"I had to do this and learn some lessons. And I hope perhaps he will move away from the presidential system he has adopted and move more towards sharing out the responsibilities and perhaps lessening the stress on himself."

Mr Wigley said it was clear that the death of the weapons expert David Kelly had hit Mr Blair very hard.

"I've no doubt that this must have been pulling him down and must be a factor which might have contributed."