David Cameron has hailed a breakthrough in efforts to crack down on tax evasion and "aggressive" tax avoidance.
He said an EU summit deal to move to full cross-border disclosure of tax information provided new momentum for a G8 summit he will host in Northern Ireland next month on the same subject.
Mr Cameron, backed by Germany and France, put the issue on the agenda in Brussels, and four hours of talks were said to have resolved years of obstruction by Luxembourg and Austria, where banking secrecy has so far been sacrosanct.
The Prime Minister left the summit to travel on to Paris for dinner talks with French president Francois Hollande, a staunch ally of the UK in the tax battle against corporates.
But before leaving, Mr Cameron emphasised that he personally had picked the subject for the G8 meeting, out of many others he could have selected, and the first "deliverable" had now been delivered, by the EU summit result.
"Tax evasion and aggressive tax avoidance are at the heart of the G8 summit, and there is real momentum behind this issue," he told a press conference. "We have a real opportunity to make this summer a turning point in breaking down the walls of corporate secrecy and get information on who really owns and controls companies and reform international tax rules to reflect the globalised economy. The best solution is tough global rules and standards where all multinationals make a full and fair contribution".
Referring to Luxembourg and Austria, Mr Cameron added: "Full co-operation has been blocked for a decade in the EU by a couple of countries. But the first deliverable (for the G8 meeting) Lough Erne has just been delivered." But Luxembourg and Austria's agreement remains conditional on similar moves in traditional tax havens neighbouring the EU such as Switzerland, Liechtenstein and Monaco.
And EU Commission president Jose Manuel Barroso pointed out: "The proposal was not, and it is not, the full harmonisation of the taxation systems in Europe. This is not possible, but we achieved some progress in some areas: on what I would call harmful tax measures or aggressive tax planning, or profit shifting, there were some conclusions taken by this European Council." He warned: "We have seen in the past many statements not always followed by actions. Now public opinion can check if these very important commitments (by EU leaders) will or will not be followed through. "
Mr Cameron also acknowledged that the deal was "potentially, as with all these things" a real breakthrough. Tax evasion and aggressive avoidance would only be resolved "when we have proper, solid, concrete action".
He added: "Tax evasion is illegal and those responsible should be treated harshly. Aggressive tax avoidance, people say, is within the law. Of course governments should move to turn questionable avoidance schemes into tax evasion and make them illegal, but no government in the world can move fast enough so there is a moral issue that companies must make decisions themselves. Aggressive avoidance raises big behavioural issues for companies which they are starting to address."