Britain's most senior judges will rule if Theresa May has the power to trigger the formal process for the UK's exit from the European Union.
PM At Tory Conference In Edinburgh
David Cameron called on Scots to drape themselves in "red, white and Saltire blue'' as he set out the Conservative goal of overtaking Labour to become the official party of opposition at Holyrood.
He said his party had delivered "real devolution'' for Scotland, keeping the United Kingdom together.
Elections to the Scottish Parliament take place in two months time and the Prime Minister insisted it was only the Tories who spoke for all those who had voted against independence in the 2014 referendum
With Scottish Labour support collapsing, he said the Scottish Conservative must change from being the "effective opposition'' to the SNP at Holyrood, and instead "fight to become the official opposition''.
He said that while "it has never been easy'' for Tories north of the border, the party had the advantage of its "absolute star'' Scottish leader Ruth Davidson along with "Labour's collapse''.
The SNP Government in Edinburgh was branded "arrogant and overbearing'', he told the party's Scottish conference in Edinburgh: "Let's make this our moment. Let's drape ourselves in red, white, and Saltire blue.''
Mr Cameron said: "In 2016 when we face some really tough elections and the SNP lack any sort of scrutiny from the second largest party, we can be the ones that give Scotland the strong alternative it needs.
"That's right, we the Scottish Conservative Party. Today we are the effective opposition and for the next 62 days we're going to fight to become the official opposition.''
While Nicola Sturgeon's SNP continues to dominate the opinion polls in Scotland - with the party seemingly on track for another majority government in May - Mr Cameron said the Conservatives are the only party capable of challenging them.
"With Labour's collapse, Scotland is in danger of becoming a one-party state,'' he said.
He hit out at the SNP's "litany of failure'' since coming to power in 2007 and added: "It falls to us, the Conservatives, the only party fit to expose these spendthrift, out-of-touch, dogmatic, inept nationalists for what they really are.''
After May's Holyrood elections the Conservative leader said "we need to win the next argument: that Scotland is stronger, safer and better off in a reformed Europe''.
The referendum on Britain's membership of the European Union takes place on June 23, with Mr Cameron echoing lines from the campaign against independence as he urged Scots to vote to remain part of the EU.
By staying in a reformed EU, he said, Scotland and the UK could have the "best of both worlds'', saying the country would benefit from "all the things that are so important to us, like the single market'' but would be "carved out of all those things we don't want any part of'' such as the euro, bailouts and the open borders of the Schengen free-travel area.
Mr Cameron said: "If we left, we would be swapping that certainty for uncertainty.''
A quarter of a million jobs in "many Scottish sectors'' are linked to Europe, the Prime Minister said, arguing: "Scotland relies on the door to the single market being wide open.
"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 basic rules for global trade, that could mean tariffs as high as 13% on Scottish salmon, 40% on lamb and up to 70% on some beef products.''
Membership of the EU "helps put Scotland in the driving seat on the world's biggest issues,'' he said, and added: "On this, Scotland proves something important.
"It shows that you can be a strong, successful, proud Scot - and be part of the United Kingdom and European Union.
"Being in these two clubs doesn't diminish Scotland's identity. It doesn't make you less of a Scot, or less patriotic.''
As well as attacking the SNP he also hit out at Labour, over the party's plans to increase income tax rates in Scotland by 1p to raise almost £500 million for schools and local services
"Just as people are getting jobs, seeing their pay rise ahead of inflation, seeing light at the end of the tunnel, Labour want to start raiding their pay packets, Mr Cameron said.
He added: "We believe it is right that people keep more of the money they earn, not less.
"It comes back to that Conservative motto - there's no such thing as government money, only taxpayers' money.
"And we have another motto for Scotland, too. We believe no one should pay more tax here than they do in England, Wales or Northern Ireland.''
Labour's position on the Trident nuclear weapon system also came under fire from the Prime Minister.
Mr Cameron said: "We know the SNP has long objected to our deterrent. But now Labour seems on course to officially oppose it, too.
"Just last week Nicola Sturgeon was on the same CND platform as Jeremy Corbyn in Trafalgar Square. That's right - standing in the shadow of Nelson, arguing to leave our country defenceless, in such dangerous times.''
He added: "Their opposition to Trident puts defence jobs and our national security at risk. And, as Conservatives, we can never, ever let that happen.''
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