Although a small amount of artificial colouring does no harm, too much can cause hyper-activity, skin rashes or breathing difficulties.
Trading standards officers who surveyed takeaways across Yorkshire found that 27 per cent of them served curries that contained more than the permitted amount of tartrazine (E102), sunset yellow (E110) or ponceau (E124). In the worst cases, levels were three or four times the legal limit.
Councillor Barry Midwood, chairman of West Yorkshire's trading standards committee, said: "I urge them to take heed of the warnings, otherwise some may face significant fines when this exercise is repeated."
One restaurateur said it was unnecessary to add colourings if food was prepared properly.
Mohammed Aslam, managing director of the Aagrah Group of restaurants, said: "I believe Indian cooking should be authentic. Tomato powder, red chillies and turmeric should give sufficient colour. Takeaways need educating not to use artificial colours excessively and customers should ask if they have been used."
Trading standards officers are due to take enforcement action against some premises using too much artificial colour.
Rotherham and Doncaster came out worse in the survey - but in the York, East Riding and North Lincolnshire council areas all the takeaway food shops passed all the colouring, hygiene and quality tests.