The former Labour prime minister also said he must carry the can for the "winter of discontent".

Lord Callaghan was in office from 1976 until he was defeated at the 1979 General Election by Baroness Thatcher.

Speaking in an interview with The Oldie magazine, Lord Callaghan said he would not be surprised if he was considered the worst prime minister since Sir Robert Walpole, who was in office between 1721 and 1742.

He said: "I think we are all re-evaluated as time goes by and I should not be the slightest bit surprised if there is another evaluation after I die and people come to the conclusion that I was the worst prime minister since Walpole."

'Crisis? What crisis'

Lord Callaghan, now 87, also said he would have taken more "initiatives" than he did during the "winter of discontent" of widespread trade union action in 1978-79.

He conceded he had been "insensitive", especially over his comments which led to the famous headline in The Sun: "Crisis? What crisis?"

Lord Callaghan never actually uttered those words, but the phrase nevertheless went down in history as his response to a reporter on returning from a summit in sunny Guadeloupe at the heart of the crisis.

The reporter had asked: "What of the mounting chaos in the country at the moment?"

'It was my fault'

The then prime minister replied: "I don't think that other people in the world would share the view that there is mounting chaos."

But in his latest interview Lord Callaghan, now 87, said: "It was my fault in the sense that I was the leader of the country.

"I was the prime minister and we had got ourselves into a position that was really disgraceful. It was probably a combination of weak leadership among the trade unions and insensitivity on my part, but I must carry the can.

"I very much regret it. Even at my present age if I were to go back and be prime minister now I would certainly take more initiatives than I did then."