SCOTTISH Green MSPs will only support the SNP’s budget if it includes the “progressive use of newly devolved tax powers, to raise the revenue needed to protect public services and investment”.

Delegates at the party’s annual conference in Edinburgh overwhelmingly passed a motion mandating their six MSPs to walk away from propping up Derek Mackay’s budget unless it includes a tax hike.

The motion passed said: “Refusal by the Scottish Government to make further use of the powers available to it is unacceptable”.

Co-convener Patrick Harvie said: “Greens are leading the change in so many ways, but on income tax it’s our progressive proposals that have truly shifted the debate.

“With the powers Scotland has over rates and bands we can do so much more than simply tweak the basic rate, as some parties have suggested.

“We can instead cut tax for low earners, raise it for high earners, and altogether generate extra funds for public services.”

Harvie also said the party would not support the budget unless there was a real-terms pay increase in line with inflation.

Speaking to BBC Sunday Politics Scotland, he said: “They have said they will lift the one per cent pay cap. That is not the same as a real-terms increase.

“With inflation going up, we really need to push the SNP much further than they’ve gone on this.

“Lifting the pay cap would still imply a below-inflation increase. That means a real-terms pay cut.”

When it was pointed out that a real-terms rise would mean one of more than three per cent, Harvie reiterated his party’s position and added: “That’s the position that the trade unions are pushing as well. They are in negotiation on behalf of their members with the Scottish Government, but I want to support the basic principle that the people delivering our public services – services that every one of us depend on every day – deserve to have their wages protected rather than eroded even further.”

Scottish Tory economy spokesman Dean Lockhart said: “Patrick Harvie’s list of unrealistic demands is getting ever longer.

“He is holding the SNP to ransom on the budget and in the process dragging them to the far left of Scottish politics.”

Scottish Labour MSP James Kelly said: “Labour put the public-sector pay cap on the political agenda in Scotland – and we welcome this commitment from Patrick Harvie to vote against a budget that doesn’t deliver a real-terms pay rise.”

The government will publish its draft budget on December 14. As the SNP do not have a majority in Holyrood, they need one of the other parties to back their spending plans.

The Scottish Greens conference also a voted for a motion calling for the devolution of immigration and asylum powers to Holyrood.

External Affairs spokesman Ross Greer said it was important for his party to “send a message that Scotland remains a welcoming country.”