The warning comes as new figures from the Cancer Research Campaign show that it is now the most common form of the disease in Northern Ireland.

The CRC predicts that over the next five years this trend will follow in Scotland, Wales and the north of England.

This is because although many men are giving up smoking and thus reducing their chances of developing lung cancer, they are failing to improve their diet. Bowel cancer has been linked to lack of fibre in the diet.

Chip warning

Professor Gordon McVie, CRC director general, said: "We know that cigarettes can kill.

"Perhaps it is time that chip butties and fry-ups also carried a government health warning.

"It is desperately sad that the same people - those of us who are less affluent - are most at risk from both of these two big killer cancers.

"The smoking messages are clearly getting through. People now need to be persuaded that simple changes to what we eat can save lives too."

Previous research shows that only two out of 10 people in the UK realise that diet plays a part in the development of cancer.

And only the same proportion achieves the recommended daily intake of fibre.

Diet is the key

Experts believe that up to one in three of all cancers are related to diet.

There are more than 30,000 new cases of bowel cancer in the UK each year, and about 18,000 people die of the disease.

Professor McVie said: "Bowel cancer is the second most common cause of cancer deaths in the UK but is probably the most embarrassing to talk about."

Professor McVie said some people were genetically susceptible to developing the disease.

"But until we are able to detect who may be at high risk, it is wise that everyone eat a high fibre, low-fat diet with plenty of high-fibre breads and cereals, fruit and vegetables.

"If you notice any of the tell-tale signs, get yourself off to the doctor straight away," he added.

The chief signs of bowel cancer are a persistent change of bowel habit lasting six weeks, rectal bleeding without any other symptoms such as soreness and irritation, unexplained anaemia, a lump in the stomach which can be felt by a doctor, or chronic severe abdominal pain.

Many of these symptoms can occur as a result of other, more minor, conditions such as irritable bowel syndrome or piles.