By politics.co.uk staff
Countries that fail to reform their tax-haven status will face international sanctions; world leaders are set to declare at the G20 summit in London.
Ministers have told inthenews.co.uk that tax-havens face "consequences" if they do not comply with new regulations being drawn up.
Chancellor Alistair Darling explained there was a "real determination for concrete action".
"Today we have had a very good discussion continuing on from the last two or three weeks.
"In it there has been a complete mood change among countries that possess tax-havens; countries are becoming more open."
But Mr Darling defended Britain's own record on favourable tax arrangements, insisting that individuals and countries were entirely separate issues.
He said sanctions against tax-havens were only "one part" of a package of measures being drawn up.
"The world expects," he said. "And we have to deliver."
Earlier, financial secretary to the Treasury Stephen Timms had declared that the "era of banking secrecy is over".
"There is a firm agreement to maintain pressure [on countries that do not submit to the new tax-haven regulations]," he said.
"Ultimately we are looking for a tangible outcome."