The EU's Big Six joined forces on Friday in a bid to claw back a hoped-for trillion euros each year of unpaid taxes by sharing customer bank data across borders.
The finance ministers of Germany, France, Britain, Italy, Spain and Poland staged a joint press conference in Dublin seen as an attempt to persuade Austria to abandon its opposition to changing strict bank secrecy laws.
Changing tax law across the European Union requires all member countries to give their approval, without exception.
Austria said the drive was simply "government snooping."
The ministers said the push would be taken around the world through international bodies at upcoming IMF, G20 and OECD meetings.
They presented it as a government fightback against money-laundering and fraud.
"This fight, this is not only national, a European fight -- but a fight at the global level," France's Pierre Moscovici said.
"Our message to those who try to evade taxes is this: places where you can hide are getting smaller and smaller," added Britain's George Osborne.
France reiterated at the talks a threat to blacklist Austria. Firmly on the defensive, Vienna in turn pointed an accusing finger at British Crown Dependency tax havens such as the Cayman Islands.
Austria is seen as the last EU holdout after Luxembourg -- the other EU banking haven that blocked legislation in this area for years -- indicated a readiness to lift some barriers in 2015.
Austrian Finance Minister Maria Fekter said Vienna would "stick to" a constitutionally-guaranteed protection of privacy for deposit-holders.
Automatic sharing of account data "is a massive intrusion of privacy," and the result would be governments "snooping in the affairs of depositors," Fekter warned.
She said that EU partners would be better served focusing on the British territories in the Caribbean and elsewhere.
She cited the Cayman Islands, the Channel Islands, Gibraltar and Virgin Islands as "the real hot spots for money laundering and tax evasion."
Inspired by a 2010 US law requiring automatic reporting of bank account information, which Spain's Luis De Guindos said his government was now implementing, the group have written to the executive European Commission seeking EU-level take-up.
The issue is shooting up the EU agenda. Through a run of set-piece meetings with G20 partners, the proposal's backers hope their efforts can culminate in a change at a May 22 summit of European Union leaders turned over to the issue.
"Every year a trillion euros are lost in tax evasion and tax avoidance" in Europe, EU president Herman Van Rompuy said in a video message announcing the agenda.
But Austria can stand its ground if it chooses so.
"Every country is independent in its own tax policy -- but this means also that every country should abstain from... illegal taxation," Germany's Wolfgang Schaeuble argued.
The renewed drive to stamp out tax fraud has been launched in Europe amid widespread austerity measures to counter a eurozone financial crisis, and as a tax fraud scandal embroils French President Francois Hollande's government.
"We know that the two phenomena -- tax evasion and money laundering -- are related to one another," said Italy's Vittorio Grilli.