THERESA May should avoid eating mouldy jam as it “may cause illness,” Food Standards Scotland has warned.

The Prime Minister inadvertently kick-started a national debate when it was revealed she had told her cabinet not to throw away a jar of jam if it had gone mouldy on top.

According to the Daily Mail, during a discussion on how to reduce food waste, the Tory leader told ministers that she scrapes off the mould and eats the good preserve left underneath.

May said once the mould is removed the rest of the jam is "perfectly edible", a Whitehall source told the Mail. She also said food shouldn’t be binned just because it is past its best before date, saying shoppers should use “common sense” to check if it is edible.

Food Standards Scotland were more cautious.

A spokeswoman told The National: “Food Standards Scotland would advise consumers not to eat food that contains mould.

“Certain types of mould can produce toxins that may cause illness if consumed, particularly in vulnerable groups, including children, the elderly, pregnant women and those who have a weakened immune system.

“There is also no guarantee that removing mould from the surface will eliminate the risk as some moulds can grow into the product, leaving unseen toxins within the food that could then be consumed.”

But Dr Neil McEwan, a lecturer and microbiologist in the School of Pharmacy and Life Sciences at Robert Gordon University, said he was sympathetic to the Prime Minister's jam scraping ways.

“There’s a degree of subjectivity," he told The National.

“When I think back to when I was younger, if you were making jam at home there would always be a few bits and pieces of mould grew on the top, you just scraped it off and got on with it.

“On the other hand, if it’s absolutely hoaching, if it’s practically walking out the jam jar to get at you, I think I’d be looking at it a different way.

“The reality is the amount of sugar there is further down in a pot of jam means very few things actually grow successfully. It’s not good conditions for most micros to grow in that level of sugar.”