In the party’s manifesto, which is due to be published on Thursday, Scottish Labour is to reveal details of proposals to tax online firms.
Meanwhile, leader Anas Sarwar admitted he is in favour of “progressive taxation”, saying if extra funds were needed, he would not be adverse to increasing tax for those “with the broader shoulders” if necessary – those earning over £100,000 or £150,000.
The party has already published most of its “national recovery plan”, which includes policies such as a personal “comeback plan” for every school child and a pay rise for NHS workers.
Mr Sarwar told The Scotsman: “I support more progressive taxation.
"I do think if we are looking to increase income tax, then it's right that falls on those with the broader shoulders. But I do think that’s got to be properly timed.
"And I think given that we do have billions of pounds of unallocated money, I think that should be our focus in terms of the national recovery.
"I want us to use the powers we have to look at how we can appropriately tax, the online giants like Amazon to rebalance the economy, and use the money that is raised to help reinvigorate the high streets, and to get people back into work.
"So that's what I think our focus should be. If, and it is an if, we feel at some point in this next parliament that we still need to raise more funds in order to meet our obligations and they can’t be met by the unspent billions, or by the new tax on on online companies, or it can’t be met by our existing priorities, then we should consider tax rises for those earning over £150,000 or £100,000.
"My presumption is against that, unless we need to do it to fill our gaps around focusing on the national economy.”
He added: “There are billions of pounds of unallocated recurring and non recurring monies available to the Scottish Government right now. I don’t know what we’re waiting for.
"We need to use those billions of pounds right now, to focus on that national recovery, which is part of the jobs recovery plan which again.
"It's also an education combined plan and an NHS plan. So I think we have flexibility within the existing Scottish budget. Those billions of pounds don't require us to raise tax, we can spend those billions of pounds to start that work and recovery right now.”
Mr Sarwar’s comments come as the Scottish Conservatives pledged to reduce income tax for higher earners if they are elected in May. Scotland’s higher income tax rates and thresholds for 1.1 million Scots would be scrapped “when public finances allow”, according to the Tories’ manifesto.
There are six income tax bands in Scotland compared to four in the rest of the UK. Workers in Scotland who earn less than £25,297 pay the same or lower income tax than other UK nations. However, the intermediate rate of 21 per cent, the higher rate of 41 per cent and the top rate of 46 per cent are all higher than in other parts of the UK.