Labour leader Ed Miliband says he will write new rules to tackle corporate tax avoidance if he wins the next election, even without international agreement.
Prime Minister David Cameron will be trying to secure a deal on the issue at the G8 summit next month.
Mr Miliband told the Observer the government had "got to act" on the "massive" issue.
He said if no deal was done, he would order multinational firms to be more transparent about the money they make.
His statement follows the condemnation of Google's tax practices by MPs.
The Public Accounts Committee heard this week that Google paid £6m in corporation tax in 2011 despite sales of more than £3bn annually, as most sales are routed through Dublin.
Source: BBC News - Miliband pledges corporate tax avoidance crackdown
Even Miliband understands it's important to deal with the issue.
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