Coronation Street stars have been told by show bosses they must seek permission before changing their appearance, according to the papers.

The News Of the World reports that all cast members have been sent a memo outlining new rules which ban them from having haircuts or tattoos, or losing weight, without first asking producers.

The move allegedly comes after the image changes of several cast members caused problems with the continuty in filming.

“The memo landed through every cast member’s door,” an insider said.

“They have been told they can’t change their appearance or body shape before asking permission.

“So they can’t have a diet or a haircut – and definitely no tattoo unless they get the green light.

“Some of them are furious about it and think it is like being back at school.”

Among those who have had changes of image in the past year are Kym Marsh – who had a boob job – while Helen Flanagan, who plays Rosie Webster, had a tattoo on her thigh.

And Katherine Kelly surprised bosses by turning up with a short haircut – which writers had to pretend was because her character Becky McDonald wanted a more conservative look for her adoption battle.

Bev Callard – aka Liz McDonald – caused similar problems when she announced she wanted to lose weight for her wedding and admitted to having had Botox.

“When scriptwriters hear something like that they go into a complete panic,” the source added.

“How are they going to explain Liz’s weight loss or the change in her face?”