Alex Salmond pressed to divulge SNP's minimum pricing level for alcohol

• Nicola Sturgeon has received several requests for details.

Opposition parties repeatedly called on ministers to name their preferred figure during a heated First Minister's Questions.

The price is critical to the success of the policy – too low and it will be ineffective in preventing harmful drinking, too high and it will do massive damage to Scotland's drinks industry.

Scottish Labour, Liberal Democrats and Conservatives all oppose the policy, and at least one party must be won over for the plan to become law.

They have concerns about how effective minimum pricing would be in reducing drinking levels, whether it would tackle Buckfast consumption, which is at the heart of Scotland's dangerous drinking, and whether it would be legal in EU law.

The health and sport committee debating the bill has repeatedly written to health secretary Nicola Sturgeon requesting clarification on key issues.

Jamie Stone, the Scottish Liberal Democrats' deputy health spokesman, asked Mr Salmond: "Will he now listen to the parliament's serious concerns and commit precisely to name the price?"

Jackie Baillie, health spokeswoman for Scottish Labour, added: "The First Minister will be aware of the growing concerns over the legality of the bill. Will the First Minister now – in the interests of transparency and because he has nothing to fear – tell us when he will name the minimum price."

However, Mr Salmond replied: "Parliament will be able to scrutinise the specific price with the same energy as it is currently giving to scrutinising the policy. The price will certainly be named before any final vote."

The Scottish Government commissioned a Sheffield Study into how minimum prices from 25p to 70p per unit, would affect mortality, people's health, crime and the economy.

The most likely price is thought to be 40p, but the Scottish Government has been reluctant to commit itself to a figure before all the evidence has been brought and in case inflation changes before it becomes law.

A commitment to minimum pricing was included in the UK Lib Dem manifesto and received the backing of the Commons health select committee, chaired by Labour MP Kevin Barron.

"It does seem to me strange that parliamentary representatives in England are prepared to support minimum pricing," the First Minister said. "Some people in this parliament, in Scotland, where we have an even more serious problem are trying to dodge the issue."

However Murdo Fraser, deputy leader of the Scottish Conservatives, said: "SNP plans for indiscriminate blanket minimum pricing would penalise responsible drinkers, harm the Scotch whisky industry, cost jobs and are illegal."