Mid Scotland and Fife MSP Murdo Fraser has promised to "kill independence" and "break the SNP" if elected new Scottish Conservative leader.
The Perthshire politician, who is favourite to succeed Annabel Goldie, will outline his vision of a "new unionism" when he officially announces his leadership bid on Monday.
He will tell supporters the UK faces a "serious threat" and that the SNP's promised independence referendum will be the "central issue" of Scottish politics in the next few years.
Mr Fraser will use the speech to outline his vision of how the Tories can make their mark in Scotland against a background of an SNP majority at Holyrood and the looming independence referendum.
"Strengthening the union will be at the centre of everything I will do," he will say. "If Alex Salmond really believed in his own message, he would put his money where his mouth is and have a single-question referendum. No second question. No Salmond cop-out. Separation — yes or no.
"Then we can move on. We can be positive about Scotland and positive about the United Kingdom. We can kill independence and break the SNP."
Significantly, Mr Fraser will also reject full Scottish fiscal autonomy, under which all taxes would be set by Holyrood, describing it as "independence in disguise."
It had previously been thought he was open-minded about such a possibility, a view that could have put him at odds with Prime Minister David Cameron.
But he will say: "I support a new form of unionism. A new unionism that will give the people of Scotland the ability to shape their own future.
"A new unionism that will provide financial devolution to the Scottish Parliament, because with power will come responsibility.
"A new unionism that calls for a more decentralised United Kingdom, at ease with itself, knowing that the whole will always be greater than the sum of the parts."
He will reiterate support for the extra powers for the Scottish Parliament set out in the Scotland Bill but reject other measures wanted by the SNP such as control of corporation tax.
"But I strongly support the principles of financial devolution, where the Scottish Parliament is more responsible for the money it spends."
But SNP MSP Stewart Maxwell attacked Mr Fraser's comments.
"Before he continues with his campaign Mr Fraser might want to reconsider his language," he said. "The last politician to threaten to 'kill nationalism' saw his party lose at this year's elections and the public back a majority SNP Government.
"Scotland wants a parliament that is working hard to build a better future, to create jobs and grow the economy. Whilst opposition parties spend their time in internal leadership wrangles the SNP will next week set out a positive programme for government that will address the concerns of voters across Scotland and take this country forward."