Every off-sales retailer in the area has signed up to the scheme, which will see the sale of alcohol to under 21s prohibited between 4 p.m. and 10 p.m. on Fridays and Saturdays.

Anyone who looks under 25 will be asked for identification proving their date of birth.

The results will be evaluated after six weeks and Fife Police are optimistic that it will lead to a reduction in the booze-fuelled fights that are too often a feature in the town centre at weekends.

Cupar is the second area in Fife to try the idea, which it's hoped will achieve the same success rate as in Armadale, West Lothian, where there has been a marked reduction in drink-fuelled crime.

The scheme has also been piloted in East Wemyss and in the north of England it proved so successful that it's been adopted permanently.

By raising the age to 21 the police also hope to target those in the 18-20 age group buying alcohol for youngsters.

At Cupar Sheriff Court recently, a man was jailed for five months for buying alcohol for a 12-year-old and a 13-year-old — and in mitigation, he confessed he himself was drunk at the time of the offence.

Inspector Craig Dewar, based in Cupar, pledged that the ban would be strictly enforced.

He said: "We are delighted to have such overwhelming support for the scheme from off-sales retailers in Cupar and Springfield.

"This initiative forms an important part of a wider police strategy aimed at tackling the violence and anti-social behaviour that blights our communities, especially at weekends.

"One of our aims is to educate these youths who are involved in this type of behaviour, and we are working with the Drug and Alcohol Project Levenmouth (DAPL) to raise awareness around alcohol misuse."

As part of their strategy to clamp down on under-age boozing, last month Fife Police ran Cupar's first Bluelight Disco, aimed at 12 to 16 year-olds, all of whom are breath-tested before being allowed in.

The idea was praised by Gerard McEneany, chair of Fife Children's Panel, who said: "The kids were having a blast and realised that they didn't need alcohol to enjoy themselves.

"Banning sales to under 21s can help; however on its own I suggest it will prove pretty ineffectual.

"Prohibition didn't work in America and already we have heard of enterprising adults getting a load of cheap booze and selling it on to youngsters for a profit.

"I suspect that this is what will happen here unless the ban is part of a larger strategy that involves awareness for parents as well as children.

"As with a lot of issues affecting young people today, I cannot help but suggest that parents need to accept more responsibility.

"If parents were being fined for the drunken behaviour of their children, would we see more parents taking responsibility?

"We have an assumed culture in Scotland that alcohol is there to get people drunk and nothing else.

"We have to change that attitude to one where people can enjoy the benefits of alcohol, but that is a generational thing that will take at least two or even three generations to get to."

Meanwhile, as the restriction on sales of alcohol to under-21s is introduced, North East Fife MSP, Iain Smith, has launched an online petition against the Scottish Government's proposal to raise the drinking age for off-sales to 21.

Mr Smith said that although the Liberal Democrats agreed that radical action must be taken to tackle Scotland's "lethal relationship" with alcohol, raising the drinking age for off-sales would "demonise" every under 21-year-old as drinking irresponsibly.

He is urging people who oppose the proposals to sign the online petition, which has been posted on his website at www.iainsmith.org

Mr Smith said: "Raising the drinking age for off-sales to 21 is a totally misguided move by the SNP.

"It will introduce a presumption that an entire generation of 18 to 20 year-olds in north east Fife are irresponsible drinkers and will do nothing to improve relations between government and young people. Indeed, it could do quite the reverse.

"If Scotland is to tackle its drink problem we need the overwhelming majority of young people who drink responsibly on-side and campaigning and setting an example to their generation.

"Our online petition will run alongside the Government's own consultation and we will present the findings to the health secretary in the Scottish Parliament."