Scotland's political parties must "pick a side" ahead of a debate on income tax, Scottish Labour has said.

The party has urged the SNP to clarify its position after the Scottish Government launched a cross-party discussion on the matter, prompting speculation of a rise.

Labour analysis argues that more than £1bn of additional revenue would have been generated by its proposals to raise tax over the past two Scottish budgets.

Interim leader Alex Rowley said: "Labour believes in the principle of using the tax powers of Holyrood to stop the cuts and invest in our public services. Parties will now have to pick a side and say what they believe in.

"The SNP has failed to use the powers it has to generate the funds needed and this, coupled with Tory austerity, has left Scotland's public services and the communities they serve under intolerable pressure."

Greens co-convener Patrick Harvie said those on high incomes should pay a fairer share to improve public services in Scotland.

He said: "Greens have been leading the debate on progressive rates of income tax and it's frustrating that it's taken this long to get the Scottish Government and other parties to say they're open to the discussion.

"Nevertheless, by working together, we can see people on low incomes given a tax cut, while those on high incomes should pay a fairer share for the public services we all benefit from."

The SNP pledged to have an "informed discussion" on income tax powers in its recent Programme for Government.

Gillian Martin MSP said: "Labour need to learn that taxation is not a competition or a political game - it's about how you fund public services and support the economy whilst ensuring that those on low incomes do not shoulder the burden of Tory austerity.

"Under the SNP, taxpayers in Scotland have the best deal in the UK, with household budgets protected, quality public services and access to services like free tuition and free personal care, all of which help make Scotland a hugely attractive place to live, work and invest in."