British prime minister David Cameron told Parliament on Wednesday that he wants the country “to be part of a reformed and successful European Union” after promising a referendum on membership earlier in the day.

The Labour opposition was unconvinced. “He’s going to put Britain through years of uncertainty and take a huge gamble with our economy,” according to Ed Miliband.

Cameron vowed to call a referendum on Britain’s future in Europe after the next general election in 2015 by which time his government intends to renegotiate the terms of its membership.

The premier shrugged off warnings that the mere possibility of a British exit could rattle its economy, arguing that Euroskepticism was at “an all time high” and the British public deserved the choice. “It is time for the British people to have their say.”

He told lawmakers later in the day, “We now have a very clear approach: a renegotiation and then a referendum.” In answer to questions from the opposition, Cameron said his government was also “very clear about what we want to see changed.”

A whole series areas: social legislation, employment legislation, environmental legislation where Europe has gone far too far. And we need to properly safeguard the single market. We also want to make sure that ever-closer union doesn’t apply to the United Kingdom.

While countries in the eurozone move to closer economic and fiscal integration, Britain is “entitled,” Cameron told the BBC earlier this month, to demand changes in its relationship with the rest of the body. The euro states are “changing the nature of the organization to which we belong,” he said, so Britain is “perfectly entitled and not just entitled but actually enabled because they need changes to ask for changes ourselves.”

Labour’s Miliband keenly pointed out, however, that Cameron’s newfound support for a referendum partly addresses the mounting Euroskepticism in his own party as well as the electoral threat posed on the right by the United Kingdom Independence Party. Many Conservative backbenchers weren’t “cheering,” he said, because of the opportunity to vote “yes” in a referendum, rather because they want to leave the European Union altogether.

Last year, 81 lawmakers rebelled against Cameron and voted for a referendum when the prime minister joined Labour in opposing one. London’s mayor Boris Johnson, who is often mentioned as a possible successor to Cameron as party leader, also spoke in favor of a referendum.

Cameron may have had little choice but to call a referendum but it could still wreck his prime ministership, writes Dan Hodges in The Telegraph. If he wins reelection in two years’ time and successfully renegotiates British membership to go on campaigning for a “yes” vote in the referendum, “Cameron’s leadership of the Tory Party would at that point become untenable.” If he wins the referendum, Euroskeptic Conservative members could move against him. If he loses it, his prestige would be shattered.

If he doesn’t win concessions from other European states and fails to meet his promise of new terms of membership, Cameron’s position would be even more vulnerable.

So his course is effectively set. The 2017 EU referendum is David Cameron’s preferred political swan song. He wins the Tories an outright majority in 2015, defies his party, leads a successful “yes” campaign, finally puts to bed the issue that has torn apart the Tories for half a century and then rides off into the sunset.