Workers looking forward to enjoying a long and leisurely retirement after years of toil, may need to think again.

New research shows that brain function declines rapidly as soon as people stop work and put their feet up.

A major British study which tracked 3,400 retired civil servants found that short-term memory declines nearly 40 per cent faster once employees become pensioners.

It appears that the lack of regular stimulation takes a heavy toll on cognitive function and speeds up memory loss and dementia, researchers warned.

Professor Cary Cooper, an expert in organisational psychology at Manchester Business School, said the study confirmed previous research suggesting that if people don’t use it, they lose it.

“It makes it more likely that dementia will set in earlier,” he said.

"We know the more cognitively active you are the more it offsets the risk of dementia.

“I'm not talking about doing Sudoku but doing something completely different from your job - so if you worked in the civil service all your life, why not go and help out in a hospital or teach?

“The most important thing is to interact with people.”