Newly elected British opposition Labour leader Jeremy Corbyn indicated he would not campaign to leave the European Union in a referendum expected by 2017, in an interview.

While he stressed that his position was “developing”, when asked by BBC News whether he could foresee a situation in which Labour under his leadership would campaign to exit the 28-member bloc, Corbyn replied “No”.

“I see the way forward as how we develop the idea of the social Europe,” Corbyn said, explaining that he opposed an EU in which workers would have fewer rights.

Corbyn has long been critical of the EU and had been unclear on his position in the past.

Conservative Prime Minister David Cameron has promised to hold a referendum on Britain’s membership of the EU by 2017, and plans to campaign for Britain to remain a member subject to his securing changes to the terms of its membership.

These include restricting the ability of other EU citizens to claim benefits in Britain, and opting out of an EU commitment to ever-closer union.

Corbyn said he did not want to give Cameron a “blank cheque” on negotiations, and was concerned that the prime minister could opt out of workers’ rights agreements and environmental protection.

If he opposed the changes won by Cameron, Corbyn said he would argue for remaining within Europe to change them, something he said “would be a manifesto position up to 2020”, when Britain is to hold its next general election.