The Greens are refusing to enter formal Budget negotiations with the Scottish Government unless ministers consider new tax rises.
Patrick Harvie’s party have an effective veto on the £36 billion package after the Liberal Democrats walked away from talks over the SNP’s refusal to shelve its independence campaign.
The minority SNP administration needs another party to vote for its Budget, a draft of which is presented to MSPs on Wednesday, or it faces collapse.
It is highly unlikely the Tories, Labour or Lib Dems will back it in next year’s Holyrood vote, leaving the Greens in a strong negotiating position.
The price of their support has been named as an overhaul of local taxation, which is likely to mean tax rises for better off Tayside and Fife residents.
Finance Secretary Derek Mackay is due to unveil his tax and spending plans for 2019-20 in a statement to MSPs at Holyrood on December 12.
Scottish Greens co-convener Patrick Harvie said: “As MSPs we have been given a clear instruction from our party members that we can only enter formal budget negotiations if there is meaningful progress on local tax reform to make a fairer system that protects services and cuts inequality.”
Mr Harvie said formal talks cannot take place if the government is “not ready to change its position”.
The Greens want local tax reform to “ditch a system of taxation that asks poorer households to pay proportionally more, to adopt a fairer system of land and property taxation, to empower local decision-making, and to shift tax from income to wealth where inequalities are greater”.
Scottish Liberal Democrats leader Willie Rennie said on Sunday: “We have pulled out of budget talks with the SNP because they would not agree to even a short cessation in their independence campaign.”
Murdo Fraser, for the Scottish Conservatives, said the SNP must take advantage of the Chancellor handing them the third biggest cash boost of all spending areas in the UK.
“This shows that the SNP Government has enough cash to support our ailing public services without asking taxpayers more,” the Perthshire MSP added.
SNP MSP Angela Constance said: “If the Tories want to promise high earners a handout, they have to explain what public service they’d cut to fund it – otherwise nobody will take them seriously.
“People know that public services need investment, and think it’s fair that higher earners pay their fair share to fund our schools and hospitals.”