It is a gastronomic preference that has long divided natives of Scotland’s two biggest cities. But Edinburgh’s long-standing love affair with salt ’n’ sauce on its fish and chips has brought cries of racial discrimination from a Glaswegian.

Tony Winters, an electrical engineer, was told he would have to pay a 25p surcharge for tomato ketchup in an Edinburgh chippie. He now plans to take his complaint to trading standards officers.

The incident has prompted Edinburgh law firms to debate “saucegate”, as it has been dubbed, as a test case for Scottish human rights.

The root of the condiment controversy is Glasgow’s devotion to ketchup, or just salt, with chips and Edinburgh’s use of salt ’n’ sauce. While the ingredients of the local speciality are closely guarded, it is thought to be similar to brown sauce with added vinegar.

“I’m feeling racially persecuted because of a condiment,” said Mr Winters as he explained how he had been denied his beloved chip accompaniment. In what Mr Winters claims amounted to “racial discrimination” against a Glasgow native, he said he had been offered brown sauce for free at Edinburgh’s Gold Sea fish shop, but told ketchup was extra.

“I couldn’t believe it,” he told The Scotsman. “Every chip shop I know gives ketchup free of charge.” He added: “You can’t offer one customer brown sauce for nothing and then charge another for tomato sauce. I said I thought it was racist that if you come from Edinburgh you can get brown sauce free but people from elsewhere, who like ketchup, have to pay.”

As the debate over sauce choices rumbled across social media, Paul Crolla, the owner of the chip shop in question, defended his decision. “Fish and chips is an Edinburgh thing and people want salt and sauce on it,” he said. “If it was up to me I wouldn’t give anyone ketchup because it ruins the whole thing. Salt and sauce goes with fish and chips, anything extra should be paid for.”

Even lawyers entered the debate, with Patrick McGuire, a partner at Thompsons, claiming that he had been “stirred” by the argument.  He said: “If someone believes their rights have been infringed they have the right to test that in a court of law.”