The couple want to continue serving beer the German way

Gordon Wetzel-Stewart and his German wife Petra run their West Brewing Company using German methods and serve beer in litres, as the Germans do.

However, the law states that although some products are served in metric, beer must still be served as pints.

The couple have said "the law is an ass" and have asked for a compromise.

Mr Wetzel-Stewart said his customers at the Glasgow Green pub, which he described as the first German brewery in the UK, like having their drinks served by the litre, in authentic German glasses.

Spirits and wine have to be sold in metric and I even have to pay my beer duty in metric Gordon Wetzel-Stewart West Brewing Company

"I am German-trained, we use a German brewing system and import all our malt from Germany," he said.

"Our customers like to order a Mass - a traditional German measure of beer - which is one litre.

"The problem is the legislation. Milk and beer are the only things that can't be sold in metric.

"Spirits and wine have to be sold in metric and I even have to pay my beer duty in metric."

Mr Wetzel-Stewart highlighted the 2001 case where a Sunderland market trader was convicted for refusing to sell goods in metric, continuing to use imperial measures instead.

"Yet as a brewer and licensee I can't sell glasses of beer by the litre," he said. "However, I can sell bottled beer by the litre. It's ridiculous.

"The law is an ass."

Notice served

Mr Wetzel-Stewart said he would continue to serve by the litre until he was forced to stop.

"We have asked trading standards to consider a compromise where we offer customers their beer by the pint and the litre," he said.

"If they want to pay for a pint we can then give them a pint glass."

A spokeswoman for Glasgow City Council's trading standards department confirmed that a notice had been served on the couple in response to a complaint.