Unison Scotland urged the Scottish government to ban companies involved in tax-dodging from taking on public contracts today.
The public services union said that ministers should use their forthcoming Procurement Reform Bill to take innovative action against companies using tax havens and other forms of tax-dodging.
Scottish organiser Dave Watson said: "It is entirely wrong that companies seeking to avoid paying their fair share of tax should be awarded public contracts.
"Public bodies in Scotland spend nearly £11 billion annually through procurement. This Bill offers ways to use that spending to deliver local social, economic and environmental benefits.
"We think this is an important opportunity to do what some European cities such as Helsinki and Paris are already doing, in acting against companies using tax havens.
"Our message to the Scottish government is that they should adopt a tax justice approach, finding ways, with appropriate legal advice, to bar companies involved in tax-dodging from being eligible to bid."