Most Britons support the monarchy and do not think the Queen should retire, a survey has revealed as she approaches her 90th birthday.

Support for the Queen stepping down from the throne has fallen significantly, with the public keen for the rule of Britain's longest reigning monarch to continue, the poll by Ipsos MORI for King's College London found.

More than three-quarters (76%) of those questioned said they were in favour of Britain remaining a monarchy, with fewer than one in five (17%) backing a republic.

And three-quarters of people (75%) said they thought the monarchy had an important role to play in the future of Britain.

Public backing for the Queen's retirement has fallen since 2001, when one-third (34%) thought she should step down from the throne.

In the most recent survey, just one in five (21%) said she should abdicate at some point and more than two-thirds (70%) thought she should remain Queen.

Approval for heir to the throne the Prince of Wales has improved over the last decade, but still does not match the support he had before the break-up of his marriage to Princess Diana.

Three in five people (60%) think he will make a good king when he takes to the throne, while 22% think he will be a bad king and 18% did not know.

Ten years ago, just over half (52%) thought Charles would do well in the role.

But approval is significantly lower than in June 1991, when 82% said they thought he would make a good king and only 5% said they did not.

Some 1,001 British adults responded to the telephone survey ahead of the Queen's 90th birthday on Thursday.

Roger Mortimore, professor of public opinion at the Institute of Contemporary British History at King's College London, said the survey showed "the outlook for the monarchy looks bright".

He said: "The Queen is our longest ever reigning monarch, and the public are clear that they want her reign to continue.

"She has succeeded in keeping the institution popular, and most people now think the monarchy will still have an important role in Britain's future.

"Moreover, the public are increasingly confident that Prince Charles will make a good king when the time comes."