BUDAPEST (Reuters) - Hungarian Prime Minister Viktor Orban said on Wednesday he would fight to make the European Union adopt a tougher migration policy, without which it would face the risk of more countries leaving.

Orban has blamed the migration crisis for Britain's vote to leave, a historic decision that has thrown EU politics into turmoil and unleashed a heated debate among member states on how the bloc should move forward.

A persistent critic of Brussels, Orban told a news conference that a big majority of Hungarians supported EU membership and no political parties advocated an EU exit now, not even the radical nationalist Jobbik.

However, he said migration was a watershed issue likely to redefine the nature and extent of European cooperation, adding he would "not relent" in his drive for a tough policy.

"Without clarifying the goals, we cannot talk about more or less Europe," he said on state TV. "If the discourse of more or less Europe lacks harmony it will lead to distrust."

"If we are talking about using the EU's resources to stop them (migrants) and extend control over the process, then Hungary supports more Europe. But if we want to use more Europe to bring them in... then redistribute them, then we support less Europe and want to keep the issue in national control."

He said that the migration issue was so important that the EU could not afford to impose its will on members without running the risk of more countries following Britain's lead.

"We must strive to guarantee that Brussels hears the voice of the citizens, that it is possible to achieve in Brussels a migration policy that meets people's wishes and does not make it unavoidable to risk their membership to step up against a migration policy they dislike," Orban said on state TV.

"If one day the people think their country can only stop Brussels' migration policy by exiting the EU, there will be trouble, because the way I understood (Prime Minister) David Cameron's words that's what happened in the UK."

Hungary plans to hold a referendum in September or October on whether it should reject any future mandatory quotas from Brussels to resettle migrants arriving en masse from countries such as Syria.

"Hungarians believe that a clear indication of their will could help create a migration policy in Brussels that is acceptable to us and therefore the issue of membership will not have to be raised," Orban said.

(Reporting by Marton Dunai and Krisztina Than; Editing by Mark Trevelyan)