The Channel 4 poster campaign promoting the ‘Big Fat Gypsy Wedding’ series will be probed by the advertising watchdog, despite a previous ruling not to.

Gypsies and Travellers in Hackney mounted a protest against the “stigmatising” publicity in February, complaining it was offensive and racist.

The slogan “Bigger Fatter Gypsier” was emblazoned on billboards across the UK, alongside pictures of children and half-naked girls.

They publicised the second series of the massively popular show, which attracted more than seven million viewers last year, and follows Gypsy and Traveller brides as they plan for their wedding day.

“What does “Gypsier” mean in this context and what do the images say about being a Gypsy?” asked a collective letter of complaint from London Gypsy and Traveller Unit in Westgate Street (LGTU), hand delivered to Channel 4’s head office in Westminster.

“We wonder if Channel 4 would have been so ready to use adverts with similarly compromising images and phrases like “Jewisher” or “more Asian” or “Blacker”?”

Christine Crawley, an Irish Traveller who lives in Lower Clapton said the posters made her feel sick, and her daughter had even been called a “prostitute” at school because of the way the Channel 4 programme portrayed her community.

The Advertising Standards Authority (ASA) which received 372 complaints announced it would not to investigate the ads, but has now made a u-turn, saying their original decision was “flawed.”

The move comes after the Independent Reviewer of ASA adjudications, the ASA Council, noted the original decision was made without realising the Irish Traveller Movement of Britain had complained and that “this was a material fact to which they should have had regard.”

Gill Brown from the said it was of “significant importance” to Travellers and Gypsies who had felt racially demeaned by the ads.

“The ASA didn’t even seem look at the complaints, and it was almost automatic they made a decision they couldn’t pursue it and sent the same response to all these people, instead of reading their letters and answering their points individually,” she said.

“I think this backlash began because of the initial article in the Hackney Gazette, the issue was picked up nationally and there was a huge amount of publicity generated,” she added.

A spokeswoman for Channel 4 said: “We will await the outcome of the investigation.”