The youth wing of the SNP yesterday lost its battle to force the government to back down on its plans to outlaw off-sales of alcohol to those under the age of 21.

The party conference in Perth held a full vote on the controversial issue, eventually voting down an amendment scrapping the proposal by 190 votes to 131.

However, it is increasingly clear that the government is likely to modify its proposals from a universal ban to a power to allow local authorities to implement such a limitation locally.

The script yesterday was that the government had to stand by the full proposal, even when the party's own youth wing joined a host of opposition party members in scorning it as illiberal and inappropriate.

Graeme McCormick, from Helensburgh, opened by saying: "Whatever views we have on individual aspects of these plans to tackle the scourge of alcohol in the country, our government deserves credit for having the guts to tackle the problem. The other parts of this policy are past dispute."

He claimed Labour deserved to suffer withdrawal symptoms for being "drunk with its own power for so many years". He demanded an end to two-for-one drink promotions and said: "The key to challenging this scourge is by throwing ideas into the pot."

He was backed by Health Minister Shona Robison, who said: "An effective policy often has to be a radical policy. Critically, this has people talking, and a good thing too."

She praised the party's youth wing, Young Scots for Independence, for arguing their position and replying to the public consultation on the issue, something which the main Opposition parties had failed to do.

"Labour say they are soft on booze, tough on caffeine. It's not good enough," she said. "I am confident that we can balance the rights of young people with the rights of those who suffer from anti-social behaviour."

But Glasgow councillor Alison Thewliss spoke against the off-sales part of the plan. "This is no criticism of the government because we support the measures generally, but a majority of young people are responsible drinkers. The problem is irresponsible selling."

Former MSP Fiona McLeod backed her, saying: "Demonising young people will not help alcohol's disgraceful relationship with Scotland. We need to offer a helping hand, not deliver a skelp."

Liam Hannen, of Blairgowrie, attacked the plan, saying: "Discrimination in any form in our society is unacceptable."

But a serious blow to the critics was delivered when one of their most influential supporters, Borders MSP Christine Grahame, said that while she supported the broad arguments of the youth wing their motion was far too sweeping to command support.

She said that for the concept of the ban to work it would have to be based very strictly on a public order argument, based on a tripartite view of the public, the police and the licensing authorities.

Falkirk West MSP Michael Matheson said it was vital to back the police and fire authorities who believed such a reform had merit, as demonstrated by a pilot project in Stenhousemuir.

Ms Robison pleaded: "Don't tie our hands, support government ministers on this," resulting in a majority of just under 60 for that position after a card vote.

Justice Secretary Kenny MacAskill said in his speech after the debate: "There is something perverse in our land when a two-litre bottle of high strength cider costs less than a bottle of water. Those who peddle it need to be regulated. Selling alcohol is not a right. It carries a responsibility.

"This government will not shirk from its responsibility to get Scotland back on an even keel with the drink. Irresponsible promotion and irresponsible pricing of alcohol is simply unacceptable."

Mr MacAskill, like the Finance Secretary John Swinney earlier in the day, took time out to pay tribute to Professor Sir Neil MacCormick, the international legal expert and former MEP who is gravely ill. He urged delegates to pay tribute to him by pouring their efforts into campaigning in Glenrothes.

Meanwhile, the SNP paraded its 15,000th member as evidence of what it claimed was growing support. Andrew Pyle, who celebrated his 18th birthday yesterday, was presented with his membership card by First Minister Alex Salmond during the conference.

The politics student at Stirling University said: "I have wanted to join the SNP for some time and getting my membership card from the First Minister is a great bonus."