The prince, who will become Supreme Governor of the Church of England when he becomes king, has already said that he wants to be Defender of Faith - not Defender of the Faith - when he accedes to the throne.

Lord Carey's comments will set him and the prince against Dr Rowan Williams, the current Archbishop of Canterbury, and other senior figures in the Church of England. Dr Williams has emphasised the need for Prince Charles to defend the Church of England when he becomes king.

In a television interview to be broadcast later this month, Lord Carey says: "When the time comes for the next coronation there's got to be a number of changes. Very significant changes. The Queen came to the throne at a time when the Church of England was really the only Christian faith in the country.

"And there were no Muslims, Sikhs, Hindus around to be in any way evident in the life of the country. Now it's a completely different world, so the coronation oath would have to be looked at more critically.

"It's got to be a much more interfaith coronation service next time around. Prince Charles put his finger on it and there's no way in which the sovereign can be defender of one faith. Although I hope that the next coronation will say very firmly that Christianity is still the dominant faith of the United Kingdom... it's got to be a much more inclusive character."

Lord Carey, 75, who remains an influential figure within the Anglican Church, made his comments in a television interview with Gyles Brandreth, the broadcaster and writer, for Channel 5.

His comments follow a Home Office report, aimed at tackling "religious discrimination", which said that a coronation oath in which the monarch swears to uphold the Protestant faith may not be appropriate in modern, multi-faith Britain.

Lord Carey's comments are likely to be welcomed by Prince Charles. He caused controversy in 1994 when, in an interview with Jonathan Dimbleby, he told of his desire to be Defender of Faith rather than Defender of the Faith.

However, one senior royal aide cautioned against any suggestion that the prince would fail in his responsibilities to the Church of England. "While the Prince of Wales believes in faith, he is a devout Christian and an Anglican," he said.

Lord Carey's comments are unlikely to be welcomed, however, at Lambeth Palace. In an interview in 2003, Dr Williams warned the prince that he must stick to his duty to defend the Church of England. "Unless something really radical happens with the constitution, he is, like it or not, Defender of the Faith and he has a relationship with the Christian Church of a kind which he does not have with other faith communities."

The crowning of the sovereign has taken place for almost 1,000 years at Westminster Abbey. The new king or queen takes the coronation oath which includes a pledge to maintain the Church of England.

In his interview, Lord Carey also reveals that he thinks that the Queen may abdicate if she becomes seriously ill. His views will surprise many royal officials who have always insisted that the Queen would rule until she dies. Lord Carey says: "I think the only thing that would make her abdicate would be if she became ill, or too incapacitated to do [the role] to the full level of her ability.

"And I could see her one day thinking, 'Well I'm not doing my job well, I don't want to be a Queen Victoria in my old age just going through the motions'."

Lord Carey reveals that after Diana, Princess of Wales died in 1997, he and Dr David Hope, the then Archbishop of York, had a crisis discussion and considered making a public statement to defend the Queen against criticism that she had not made a public appearance.

"I consulted with the Archbishop of York and we felt there was no point in coming out into the open, because it would only make matters worse." Lord Carey insisted that the Queen was "devastated" by Diana's death.

Lord Carey said he was upset by Earl Spencer's speech at the princess's funeral. "I was quite opposed to him giving that address. I didn't feel it did justice to his sister... it wasn't fair to the Royal Family... My feeling is that [the Queen] wasn't happy at all about that address and would have liked something that was spoken of Diana's faith."

END