In an interview to mark his 90th birthday, Lord Callaghan has predicted that the Conservatives will return to power.

His warning to Labour ministers is: "The pendulum swings and it will swing again."

Callaghan, who was prime minister for two years until 1979, also admits his envy at Tony Blair's majority in the House of Commons.

"I think he has made a great success, our dashing prime minister. It would be foolish to attempt to deny that. He has had a great victory and I wish I had had a majority, that would have made things a lot easier," he told the Press Association.

The Labour government had no majority in the Commons during Lord Callaghan's time in Number 10, continuing to govern through a pact with the Liberal Party.

"We kept the ship afloat. The government had to be carried on. Everybody helped and there were no grumbles. I enjoyed it, until the last six months when it overwhelmed us," he said.

Speaking of his time as a member of the Westminister parliament, he describes himself as "a professional politician."

"It was a life of service. I have enjoyed it and I am very sorry that today politicians now stand in such low regard," he said.

"I was very lucky in many ways, by being in the right place at the right time. I feel very blessed. It is nearly 25 years since I was prime minister. I have had a long time to think. I have been able to learn a lot in that time. I wish I had thought about them earlier."

Callaghan was the first politician to reach Downing Street after holding three major cabinet posts; chancellor, home secretary and foreign secretary.

"The Treasury was the most stressful of my offices," he admitted.

"The Home Office was in some ways the most rewarding and certainly challenging partly because of Northern Ireland. I was in charge of Northern Ireland then.

"And the Foreign Office I regarded as the most fascinating and at the same time the most frustrating. It was fascinating because of G7, the meetings of heads of government of the main industrialised nations and frustrating because of issues like Cyprus.

"But above all, the prime ministership, because it was exhilarating, the most stimulating all-round office you could possibly find."

Lord Callaghan also commented on the recent ill health of his successor, Baroness Thatcher.

He said: "I hope she will be all right. At 76, she is still a chicken. I hope she has many more years to go."

Tony Blair described Callaghan as "one of the dominating political figures over the last half century."

"Throughout his political life, too, he has been driven by Labour - and Welsh - values of social justice and opportunity for all. Typically even after his retirement as an MP, he continued to make a real contribution in the pursuit of these goals as a Labour peer in the Lords," he said.

"Lord Callaghan became Prime Minister at a very difficult time. Anyone who has the privilege of taking on the job quickly realises its difficulties and pressures.

"For his strengths as a politician also rest, of course, on his strengths as a man. I, like many other people, know from personal experience of his wise advice, his loyalty and his kindness," he added.

Writing in the current issue of House magazine, Lord Morgan said of Lord Callaghan: "On issue after issue, his government blazed the trail for New Labour.

"For Don Bradman, 90 not out simply led on to the century. So may it be with Original Labour's Big Jim."