It is not the first time an Irn Bru advert has been criticised

The advert shows children singing with their mother before she ends the song "even though I used to be a man".

The children stop singing and look dumbfounded at their father. The mother is then seen in the bathroom, shaving her lathered face.

In total, 17 viewers complained to Ofcom that the advert, set in the 1950s, made fun of transsexual people.

The watchdog agreed that the shaving scene was in breach of the Advertising Standards Code.

'Negative stereotypes'

It "could be seen as directly mocking transsexual women and was capable of causing offence by strongly reinforcing negative stereotypes", it said.

The advertisers said the mother was portrayed as proud and unashamed of her operation and the joke was not at the expense of transsexual people but at how attitudes have changed over time.

But the watchdog said that the initial scene of the family singing around a piano was not likely to cause offence.

Ofcom also ruled that another advert featuring a transsexual person, for Walls Cornetto, did not breach the advertising code.

The advert showed a young woman in a bikini trying to persuade a male friend to hand over his ice cream.

When he asks what's in it for him, she answers: "I'm a man, surprise, give me Cornetto and I won't tell the guys."

But Ofcom said the Cornetto advert did not show transsexual people in a negative light.