The scientist, writer and inventor coined the maxim "early to bed, early to rise makes a man healthy, wealthy and wise".

Franklin was not alone in his belief in the benefits of going to bed and rising early. The inventor Thomas Edison believed that too much sleep was bad for health and slowed the progress of civilisation, while the writer Samuel Johnson warned "nobody who does not rise early will ever do any good".

But researchers from Southampton University have found that night birds who sleep in late suffer no ill effects from their supposedly unhealthy lifestyle. In fact, they may be wealthier than "larks".

Benjamin Franklin: Proved wrong

The Southampton team studied 1,229 men and women over 65 years of age who took part in a Department of Health survey in 1973-1974.

They did uncover bad news for those people who like to linger between the sheets.

In the 20 years following the original study, people who admitted to spending 12 hours or more in bed were one-and-a-half times more likely to die slightly younger than those people who limited themselves to nine hours shut eye.

The researchers had no explanation for why excessive sleeping should increase mortality, but they said their data ruled out a simple link between illness and sleep.

Fallible advice

Writing in the British Medical Journal, the researchers, Catharine Gale and Christopher Martyn, said: "Our results suggest that, though it may be wise not to spend much more than eight hours in bed each night, the time of going to bed and getting up matters little.

"It seems that owls need not worry that their way of life carries adverse consequences.

"However, those who cite Franklin's maxim to encourage their children to go to bed early may wish to consider whether their practice is entirely ethical."

Dr Martyn told BBC News Online that he had carried out the research to prove that supposedly wise counsel - whether it be in the form of proverbs or medial advice - was not always infallible.

"The main message of our study is that you should go to bed when you like and get up when you like," he said.

"If your natural biological rhythms lead you to stay up late, and get up late, then do that.