Soros announced Tuesday that Best For Britain, a campaign to secure a second referendum on whether the U.K. should leave the EU, will launch its ‘manifesto’ on June 8. The manifesto will reportedly include a roadmap for stopping Brexit.

The campaign, which was created by Gina Miller last year, has already received millions of pounds in donations according to The Guardian, including £500,000 (approx. $663,000) from Soros. It aims to persuade members of parliament to require a new referendum on the final withdrawal deal. In order to do so, it will focus on engaging with voters, and Brussels as well.

In a speech at the European Council on Foreign Relations, a think tank Soros helped found, the billionaire said that “Best for Britain fought for, and helped to win, a meaningful parliamentary vote which includes the option of not leaving at all.”

“But the British public must express its support by a convincing margin in order to be taken seriously by Europe. That’s what the Best for Britain is aiming for by engaging the electorate,” he continued.

Soros explained that “Brexit is an immensely damaging process, harmful to both sides.” While he acknowledged that “it’s up to the British people to decide what they want to do,” he pointed out that “it would be better…if they came to a decision sooner rather than later.”

Despite supporting the U.K. remaining in the EU, Soros did concede that the EU is facing “an existential crisis,” due in no small part to the ongoing political crisis in Italy. He therefore argued that “the EU needs to transform itself into an association which nations like Britain would want to join.”