THE No referendum campaign that saved the United Kingdom has opened up "a huge political opportunity" for the Conservatives to make gains in Scotland, David Cameron has said.

The Prime Minister last night praised Scottish party leader Ruth Davidson, whom he described as "a total star". He told her that through all the debates and television interviews "you impressed everyone with your composure but, above all, with your passion".

At a packed Scottish fringe meeting of the Conservative conference, Mr Cameron insisted the party had taken on "all the big arguments" and won.

His comments came after Chancellor George Osborne had outlined in his keynote speech how 10 million households would have their benefits frozen if the Tories were returned to power next May. Jobseeker's allowance, child benefit, tax credits, income support and housing benefit would be frozen for two years from April 2016.

Meanwhile, Mr Cameron pointed out that the UK Government could have ducked the independence issue and allowed Alex Salmond to have illegal referendum after illegal referendum and "rather cowardly ... break up the Union by stealth".

"That was not the choice we made. We said one question, one referendum, fair, legal and decisive. Let's just say now, loudly and proudly, it was the right call and we saved our United Kingdom," said the PM to cheers and applause.

He stressed the vow made on further devolution to Holyrood would be honoured, saying: "A Conservative government will deliver those tax powers, those spending powers, those welfare powers that we promised. We should be proud of what we are going to do."

But the Tory leader added: "We have a huge political opportunity here. We've now got a leader with huge stature and following in Scotland. We've now got a database of not just Conservative supporters but of friends of the Union, who look to us to defend our United Kingdom.

"We've got people who've been hardened in the battle and in campaigning."

The PM watched the votes come in at 4am on TV in the No 10 press office. His son Arthur Elwen was wearing tartan pyjamas.

He said: "They knew how worried their dad was and they cared deeply about it too." Mr Cameron said it was a relief "going to bed as Prime Minister of the United Kingdom and waking up as Prime Minister of the United Kingdom."

The party's targets include the lowlands, highlands, Fife, Argyll, Aberdeenshire and Perthshire a

He added: "We've got the people, we've got the message, we've got the leader, now we can really turn the next 200 days into the opportunity to win more Conservative seats in the Westminster Parliament for Scotland."

A ministerial colleague emphasised how the Scottish Tories were now "back in the game."

But former leader Baroness Goldie warned Conservatives of lending their votes to the SNP, describing it as a "dangerous liaison."

Ms Davidson will today say the that Tory Party has found its voice north of the Border.

"The last two years have proved that, far from being 'toxic', it was the Scottish Conservatives who spoke up for Scotland's silent majority."