The Scottish Tories will be the "real alternative" to the SNP in next year's Holyrood elections, Conservative leader Ruth Davidson said.

With 150 days to go until the Scottish Parliament elections, Ms Davidson criticised both the SNP and Labour.

She said the Conservatives would be "an alternative voice which will stand up to the SNP's plans for separation and constant flirtation with a second referendum".

She also insisted Labour had "comprehensively failed" in its role as the official Holyrood opposition, saying: "With Labour in such disarray, many people are worried - deeply worried - that Scotland is becoming a one-party state."

The Scottish Tory leader made a speech in Edinburgh in which she said her party's election campaign "really gets going" later this week when its regional lists for the election are revealed.

Tory selection procedures have been reformed since Ms Davidson became Scottish leader as she said she wanted the "brightest and best at our parliament".

Tens of thousands of Conservative supporters have helped rank hundreds of regional-list candidates in what Ms Davidson said was the "biggest exercise in grassroots democracy this party has ever undertaken".

The slump in support for Labour means the Conservatives are now competing with them to be the second party in Holyrood behind the SNP.

Ms Davidson said: "Whoever comes forward, I know I am going to have a heavyweight team around me who are united in wanting to give something back to this country."

She also insisted the forthcoming election campaign would be "planned, executed, organised and run from here in Scotland".

The Tory said: "I don't need to go to London and have David Cameron do a photo-opp signing a wee piece of paper to tell me that I'm in charge. And he doesn't need it either.

"Ours is a party that now gets devolution and has transformed itself to reflect entirely our modern union.

"This is a Scottish election. So, this is our campaign. It's our plan, policies and ideas. Made in Scotland. For Scotland."

The Tories will set out more detail on policies after new year but she said the main issues for the election would be taxation, services and the constitution.

With Holyrood due to get some responsibility for income tax powers in April, and with more powers to follow as a result of the Scotland Bill, she said this was the election in which Scottish politics would "get real".

She warned if the new powers are not used wisely "public services will suffer", adding: "This isn't a time for gesture politics. It's time for cool heads and sensible stewardship.

"The priority should be grow our tax base, to expand our economy and get more high-value jobs. That way we all benefit. But here's the thing: none of that will happen if we throw up a warning sign over Scotland saying 'higher taxes here'."

A Conservative commission on taxation, headed by former CBI Scotland director Sir Iain McMillan, is due to report back within the next few weeks.

Ms Davidson stressed: "Our principles are already set: Scotland will only lose out if we increase the tax burden above the rest of the United Kingdom."