David Cameron has launched a stinging attack on the SNP's "litany of failure" in government and has backed the "Sturgeon-slaying" Scottish Conservative leader, Ruth Davidson, to become the official leader of the opposition.
Speaking to around 800 delegates at the Scottish Conservative conference at the home of Scotland's rugby team, Murrayfield Stadium, the prime minister threw his weight behind Davidson as she bids to supersede Kezia Dugdale's Scottish Labour and achieve the party's best ever election result in May.
"We have a not-so-secret weapon," said Cameron. "A formidable force in politics, our Sturgeon-slaying, Dugdale-defying, absolute star of a leader, Ruth Davidson."
He added: "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."
Cameron condemned Nicola Sturgeon's SNP for what he called a "litany of failure" since they became the party of government in 2007 and said, following the "collapse" of Scottish Labour, the Scottish Conservatives are the only party who can "keep [the SNP] in check".
"We're the party that can challenge the SNP, and now the only party that can challenge the SNP," said Cameron. "They've been in power for 9 years, they are the establishment, and with Labour's collapse – Scotland is in danger of becoming a one-party state."
He reeled off a long list of what he called "SNP failure", accusing Sturgeon of cutting help for poorer students and failing to increase health spending, and he criticised the "mess of the law which bans football songs", and the "abolition of right to buy".
However, Cameron reserved his strongest criticism for the SNP's "named-persons" policy which allocates each child in Scotland with a guardian.
"I'll tell you who needs a guardian – someone to keep them in check – it's the SNP. And 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."
Cameron outlined four messages he thinks will make people in Scotland vote Conservative in May: that they are the "only party of the Union" between Scotland and the rest of the UK, that Scotland is safer in the European Union, that the party supports the renewal of the UK's nuclear weapons, and that it opposes tax rises.
He said Scottish Labour's proposal to raise the rate of income tax but hand back a rebate to those on the lowest incomes was "classic Labour", adding: "dock people's pay, hand some money back to them – and then ask them to thank you for it".
The prime minister also condemned Sturgeon and Labour leader Jeremy Corbyn for appearing at the same anti-Trident rally in Trafalgar Square in London last week, saying: "That's right – standing in the shadow of Nelson, arguing to leave our country defenceless.
"In such dangerous times, with Russian aggression raging, with Daesh on the rampage, their opposition to Trident puts defence jobs and our national security at risk, and, as Conservatives, we can never, ever let that happen."
On Europe, Cameron revived his "best of both worlds" message which he campaigned on during the Scottish independence referendum in 2014, and said that campaign proved it's possible to be a "strong, successful, proud Scot" while being part of wider unions of countries.
"Being in these two clubs doesn't diminish Scotland's identity," said Cameron. "It doesn't make you less of a Scot, or less patriotic. 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 where we have the best of both worlds."
He added: "So after we've won in Holyrood in 62 days, we all need to make that case for certainty for the good of everyone in this great nation."
Ahead of the conference on Thursday, SNP business convener Derek McKay said: "On his fleeting visit to Edinburgh tomorrow, David Cameron should exercise caution in lecturing Scotland – perhaps by getting his own house in order first by reversing the failing Tory agenda of further punitive cuts and damaging austerity.
"Based on his record, it's little wonder that the Tory prime minister's approval ratings are at rock bottom and his party are still reeling from their worst electoral defeat in Scotland for 150 years – under David Cameron and Ruth Davidson, the Scottish Tories are a party going nowhere."