The Scottish government’s plans to bring in minimum pricing for alcohol could fall foul of international trade laws, according to the UK’s European trade commissioner, Baroness Ashton.

Plans for a minimum price per unit of alcohol could impact on imported goods by raising their price to the same level as those made in Scotland, which would breach World Trade Organisation (WTO) and EU laws, she said in a legal analysis of the proposals.

However, the move would be legal if there was no impact on imported goods, the report added.

Ashton said other measures could be implemented to meet the public health objectives behind the proposal, such as increasing duty. Scottish ministers, though, are bound by decisions made in Westminster on duty.

“There is no question the Scottish government is stumbling into a legal minefield with these ill-considered proposals,” said Tory MEP Struan Stevenson. “We already know Scotch whiskies would get caught, demolishing Alex Salmond’s claim to be the saviour of the industry.”

The government’s plans for a minimum price of 40p or 50p per unit of alcohol is part of a bid to tackle binge drinking problems, which are estimated to cost the country more than £2bn a year.