Tony Blair has warned that British people will vote to leave the European Union if Brussels seeks greater powers over member states as a result of the eurozone crisis.
The former prime minister, who has expressed an interest in one day being an elected president of the EU, was speaking to the German newspaper Die Zeit.
He said he had "deepest sympathy" for German chancellor Angela Merkel in her struggle to keep the euro from collapsing without using German taxpayers' money to bankroll the currency, but warned that the fallout from the eurozone crisis could lead to further powers being taken away from member states.
"If more competences are transferred to the EU, then its democratic legitimacy must be built up too," said Blair. "Britain must play a strong role in this. Because we need a balance between European institutions and the nation states.
"If this is done wrongly, we could create a political crisis that could become just as a big as the euro crisis," Blair went on. "People will not go along with the abolishment of the nation state."
The Eurozone crisis is expected to enter a new phase next month, with the renewed spectre of Greece defaulting on its debts and requiring either another costly bailout or the country's potential exit from the single currency.
At the same time Spain is expected to formally request a bailout, amid fears many Spanish regions are technically bankrupt.
Despite widespread calls for the creation of "eurobonds" - the clubbing together of eurozone nations' debt - Merkel has resisted the idea for over a year, since it would see German taxpayers being saddled with southern European countries' debts.
Senior British ministers accuse European politicians of merely "kicking the can down the road" each time a new euro crisis appears, rather than tackling the cause of the structural problems in the currency.
Although David Cameron has been fuzzy on the details, it seems likely that the PM will offer voters a referendum on Britain's relationship with Europe in the Tory party manifesto for the next general election.
The PM is apparently unwilling to offer an in-out referendum, saying only that a re-assessment of Britain's place in Europe could require a national vote.
But Labour and the Lib Dems have also suggested a referendum, possibly on an "in/out" basis, which could force Cameron into offering a comprehensive vote.
Cameron has been criticised by some Tories for appearing to offer a half-hearted promise of a referendum without spelling out in terms what the question would be.
The government defends Cameron's position by saying Britain will have to wait until the Eurozone crisis has played out, to see what further political integration takes place within the Eurozone members to tackle the currency crisis.