NICOLA Sturgeon is due to publish SNP proposals on income tax reform tomorrow as part of a cross-party debate ahead of the 2018/19 budget.

As part of efforts to reach consensus at Holyrood on a more progressive tax system, the First Minister will unveil a long-awaited “discussion paper” at an event in Edinburgh.

It follows an appeal by Ms Sturgeon and Finance Secretary Derek Mackay for contributions from other parties at Holyrood on paying for public services.

The Greens, Liberal Democrats and the two contenders for the Scottish Labour leadership, Anas Sarwar and Richard Leonard, are understood to have contributed.

The Scottish Tories simply want income tax rates to be the same or lower in Scotland than in the rest of the UK.

The contributions have been costed by civil servants to show how much each would raise and on which taxpayers the burden would fall.

With the SNP also expected to include its own ideas, such as more bands, the aim is to generate debate ahead of the UK and draft Scottish budgets this month and next.

Wages in Scotland are currently taxed at 20p in the pound above £11,500, at 40p above £43,000 and at 45p above £150,000.

The SNP promised in its 2016 Holyrood manifesto that it would freeze the basic 20p rate throughout the parliament, but Ms Sturgeon recently said all rates could potentially change.

Adding 1p to each rate would raise an extra £500m a year.

The Scottish Greens initially proposed five bands with a top rate of 60p, but co-convener Patrick Harvie said last month that the party was now flexible.

Mr Sarwar yesterday wrote to Ms Sturgeon asking her to consider his plan to raise an extra £700m for services by having five bands and a top of 50p above £100,000.