The Scottish Conservatives are targeting disenchanted Labour and Lib Dem voters as they step up campaigning for the Holyrood election.

Leader Ruth Davidson is to send out a personal letter to 600,000 people, many of whom have never voted Conservative before, to ask them for support on May 5.

The party, which has 15 MSPs, said recent polling showed that 12% of Labour voters and over 20% of Lib Dem voters from last year's general election are considering voting for the Tories.

Campaigners believe they can compete with Scottish Labour to form the opposition to SNP in the Scottish Parliament.

A spokesman for the party said: "Ruth is setting out a very clear pledge to people at this election: if you want the SNP held to account, if you oppose a second referendum and if you want family finances protected, then she will fight your corner.

"We have seen support grow for the Scottish Conservatives over the last few weeks. Talking to families up and down the country, it's become clear that there are many people who haven't voted Conservative before who are now thinking about doing so.

"Many of these people used to vote Lib Dem or Labour. They supported Scotland's decision to stay in the UK. They want the country to move on from the last few years of division. And they're looking for someone at Holyrood to back them up.

"Labour and the Lib Dems in Scotland aren't dong that - incredibly, they have now said that their own candidates are free to support independence. All that will do is take the country backwards to yet more constitutional division."

Ms Davidson is to make speeches in Aberdeen and Stirling this week to set out the party's campaigning platform.

The spokesman added: "Ruth's message is that every vote for her is a vote to stop the SNP flirting with another referendum, and to start focusing on the things that matter - more housing, a growing economy, and public services built to last."

A Scottish Labour spokesman said: "The Tories have promised a revival in every election since 1997 and it hasn't happened.

"Standing shoulder to shoulder with the SNP to vote for hundreds of millions of pounds of cuts to schools and other public services isn't acting as an effective opposition - it's cutting into the future of our nation.

"Ruth Davidson wants us to believe she is a modern Tory but her tax plan is straight out of the 1980s."

A Scottish Liberal Democrat spokeswoman said: "The Tories are misguided. If they were genuinely interested in saving the union, they would try to persuade SNP voters to change their mind.

"A Conservative Party that is savagely cutting public services, is split on Europe and is hostile to orphaned refugee children is hardly an attractive prospect for any liberal-minded voter.

"In contrast, the Liberal Democrats offer positive, liberal change with a 'penny for education' which will deliver £475m for a transformation in Scotland's education."