The SNP Government faces a three-party attack on its plans to raise the age limit to 21 for buying off-sales alcohol, as the opposition sides with a student campaign to keep the current limit at 18.

The SNP Government faces a three-party attack on its plans to raise the age limit to 21 for buying off-sales alcohol, as the opposition sides with a student campaign to keep the current limit at 18.

Labour yesterday joined Conservatives and LibDems in arguing the priority should be cracking down on retailers who break the law as it stands - with test purchasing showing it is a widespread problem but few licence holders taken to court or penalised through the licensing process.

Labour tabled plans that would mean mandatory bans for retailers selling drink to under 18s. The first offence would bring a three-month ban, and if it happened again, that would rise to six months. A third time offender would be deemed unfit to hold a licence, according to Pauline McNeill, Labour's justice spokeswoman.

"Labour has always taken a tough line on alcohol abuse," she said. "We believe that enforcement against those who are currently breaking the law must be central to any strategy."

Bill Aitken, the Tory justice spokesman, said the Labour stance would make the regime softer than it is already. He said it was "ridiculous" that offending retailers should be given as many as three chances.

For the LibDems, health spokesman Ross Finnie also attacked Labour for proposing the current law should be softened: "As long as the current laws are enforced, there is no need to raise the drinking age for off-sales to 21. Our young people are part of the solution to Scotland's lethal relationship with alcohol, not just part of the problem."

Recent evidence shows only 37 retailers had licences suspended for selling alcohol to under-18s over four recent years. Last year, 83 adults were prosecuted for supplying children with alcohol.