Mr Kerr made the announcement as he published the Updated Plan for Action on Alcohol Problems, which sets out a range of prevention, education, and treatment measures.

Government will work in partnership with alcohol and drug action teams, the NHS and voluntary organisations to reduce alcohol-related harm.

Also published today were details of a new partnership to engage the drinks industry’s resources and expertise in tackling alcohol misuse.

Announcing the extension of the test purchasing scheme, Mr Kerr said, “Communities across Scotland are blighted by the problems associated with under-age drinking, and rolling out test purchasing will give us a valuable tool in the fight against this.

“I know that the vast majority of retailers take their responsibility very seriously, but we need to take action against the minority who sell alcohol without carrying out the proper checks.

“The findings of an interim evaluation report on the alcohol test purchasing pilot clearly show that the scheme can be carried out safely, fairly and effectively and we now want to replicate that success across Scotland.”

In the Fife pilot scheme, launched in June, under-16s attempt to buy alcohol from both on and off-sales premises. Those which sell are reported both to their local licensing board and the procurator fiscal.

Most premises in Fife have now been tested. The failure rate is around 17%-20% for on-sales and 15% for off-sales.

Six off-sales have had their licences suspended and one has been convicted of selling alcohol to under-18s. The first on-sales licence is shortly due to be considered by Central Area Licensing Board with a view to possible suspension.

Assistant Chief Constable Allan Burnett said the pilot scheme had been a worthwhile experience.

“While we are clearly disappointed at the failure rate, the figures reflect the fact that the majority of licencees are taking the issue of under-age drinking seriously.

“However, for those who think they are above the law, we are committed to catching them and will be calling for even tougher penalties. The consequences to their reputation and livelihood can be very serious.

“The message is simple-if you can’t tell, don’t sell.”

A spokeswoman for Tayside Police said, “We have been monitoring the Fife Constabulary test purchasing pilot with interest and we are pleased that the scheme will now be rolled out across the Scottish forces.

“Whilst we already make regular visits to licensed premises, this will give officers another innovative way of tackling under-age drinking and ensuring that both licensees and staff who work in off-sales and licensed premises remember their responsibilities when it comes to selling alcohol.”