By Jon Craig, Chief Political Correspondent
Tax havens such as Bermuda, Jersey and Guernsey will have six months to open their books or face international blacklisting if Labour wins the General Election in May, Ed Miliband has vowed.
The Labour leader has accused David Cameron of failing to follow through on demands that all overseas territories and crown dependencies adopt transparency measures being introduced in the UK.
Agreement on action to expose the owners of "shell companies" used to evade tax was hailed by Mr Cameron as a key achievement of the G8 summit in Northern Ireland in 2013.
He said then: "The UK is today leading the way by committing to create a central registry of company ownership.
"Each and every one of our overseas territories and crown dependencies has agreed to sign up to the multi-lateral convention on information exchange to exchange information automatically with the UK and to produce action plans on beneficial ownership."
But so far, according to Mr Miliband, none of the countries around the world over which Britain retains sovereignty has accepted the Prime Minister's appeal to them to "move forward together in raising standards of transparency" and some have ruled out reform.
Among the 10 countries whose leaders were called to No 10, Bermuda has rejected calls to make public the companies registered there.
So too have the Cayman Islands. Gibraltar has taken no further action. Neither has Guernsey or the Isle of Man.
In a letter to the leaders of the overseas territories and crown dependencies, Mr Miliband put them "on notice" that, if elected in May, his government would refer any that failed to produce publicly accessible central registers of beneficial ownership - who profits from a company - to the Organisation for Economic Co-operation and Development (OECD).
"I am writing to put you on notice that a Labour government will not allow this situation of delay and secrecy to continue," he wrote.
"Labour will act on tax avoidance where the Tories will not," he added, ending protection from international scrutiny and requesting OECD blacklisting.
Mr Miliband, accused this week of being anti-business, told a conference of Labour councillors in Nottingham: "The current Conservative leadership have become the political wing of offshore hedge funds.
"Unlike them, we will not stand by. We will ensure a country where everyone plays by the rules, from top to bottom."
But a Conservative Party spokesman said: "People should judge Ed Miliband by his record, not his rhetoric.
"For 13 years - including when he was an adviser in the Treasury - Labour did absolutely nothing to tackle tax avoidance. This shows that Ed Miliband is simply too weak to deliver on what he promises.
"In contrast, we are tackling the problem head-on. David Cameron put tax dodging at the top of the global agenda at the UK's G8 summit, securing major new international rules to ensure that companies pay what they owe."
