The Prime Minister said Scotland relied “on the door to the single market being wide open” when he addressed the Scottish Conservative conference in Edinburgh.
Claiming there were 250,000 Scottish jobs linked to trade with Europe, Mr Cameron said Scotland would be “better off” by remaining in Europe.
He added that his party had delivered “real devolution” for Scotland and insisted that it was now only the Tories who spoke for all those who had voted against independence in the 2014 referendum.
Mr Cameron said: “With the world wanting to drink its whisky, eat its salmon, wear its wool, buy its electronics and use its financial services, Scotland relies on the door to he single market being wide open.
“Today Scottish farmers can sell their meat, without quotas without tariffs, to a market of 500 million people. But if Britain leaves that could all change. A trade deal like the one Canada has agreed with the EU could involve tariffs and quotas on our exports and if we have to fall back on the basis rules for global trade, that could mean tariffs as high as 13 per cent on Scottish salmon, 40 per cent on lamb and up to 70 per cent on some beef products.
“I really think it’s time for those who want to leave to explain what Scotland would look like if we left and to start giving voters some of these facts.
“It’s for them to look those farmers in the eye and tell them they have to pay tariffs and, if so, how much.”
Speaking to around 600 delegates in a hospitality suite at Murrayfield Stadium, the Prime Minister urged them to drape themselves in “red, white and Saltire blue” as he argued that being for the EU and the UK was not a barrier to Scottishness.
“Being in these two clubs doesn’t diminish Scotland’s identity. It doesn’t make you less of a Scot, or less patriotic,” the Prime Minister said.
“What matters is turning patriotism into action, being able to get things done for the country you love. I believe that’s what we can do in a reformed Europe.”
The Prime Minister said being part of a reformed EU offered the “best of both worlds” – access to the single market but without the unpopular aspects of the European project such as the euro.
“Our membership helps put Scotland in the driving seat on the world’s biggest issues, and on this, Scotland proves something important.”
Ahead May’s Holyrood election, Mr Cameron portrayed Scottish leader Ruth Davidson as the one politician capable of standing up for the UK declaring that the Conservatives were the “only party” of the Union.
With the Conservatives attempting to shed their toxic brand north of the Border by capitalising on the popularity of Ms Davidson, Mr Cameron described her as a “Sturgeon slaying, Dugdale defying- absolute star of a leader”.
He said: “We’ve got Labour and the Lib Dems saying their politicians can campaign either way if a second referendum should ever take place. For Scotland this is huge.
“It leaves just one party – the Conservatives – and one person, Ruth, to speak up for the two million people who voted No in that referendum. If you love Scotland and you know that our four nations are better together, then there’s only one party for you and that’s the party in this room.”
But on Europe the Prime Minister was accused of scaremongering by Jayne Adye, director of leading cross-party grassroots Eurosceptic campaign Get Britain Out. She said: “It is unfortunate to see David Cameron engaging in even more scaremongering in Scotland, suggesting Scottish farmers are going to be worse off in the event of Brexit.
“He has ignored the key facts which indicate the EU is a market of declining importance to Scottish businesses, which are increasingly trading with the wider world.
“Between 2002 and 2013 Scottish exports to the EU – as a proportion of total international exports – declined by around 10 per cent.
“Leaving the EU will enable the UK to do trade deals with global expanding markets, which will provide far greater security and opportunities for Scotland to sell their fantastic products.”