The study says, "Even if people heed the message and put in place a written plan, they may still experience poor health or unforeseen events that can lay waste to the best retirement strategies. If workers are unable to work for long periods due to poor health or find themselves having to give up work altogether and retire early, they may have to draw on savings and investments which had been intended to fund retirement. The best retirement strategy is one that contains a backup plan."

And what's the backup plan?

Well, among the 47 percent of those who say they have one, 57 percent say it's their savings; 30 percent say they'd be relying on a spouse or partner working, which might not work out if the household relies on a double income.

Then there are illiquid assets; 19 percent say they'd rely on downsizing their home or selling a second home.

Frighteningly, 10 percent would rely on gifts or loans from family members and/or friends, while 10 percent would look to bank loans.

However, they're not all so unprepared. Says the report, "Workers also cite reliance on insurance products that have been especially designed to cover individuals in the event that they are unable to continue working, such as critical illness insurance (21 percent), income protection (19 percent), and disability insurance purchased individually or through an employer (17 percent)."

Even so, those looking to illiquid assets might have to wait a long time to sell a house or other object, while those relying on disability insurance might fail to satisfy eligibility requirements.

Clearly, workers need to do considerably more work on their Plan B.