A terminally ill British man has been granted permission to challenge the country's law on assisted dying, after an earlier decision that rejected his case.

Noel Conway, 68, has motor neuron disease. He applied to the High Court last July, asking for a declaration that Britain's outlawing of suicide is incompatible with the European Convention on Human Rights. The court rejected his bid in October.

But two judges on Thursday ruled that Conway's case should proceed.

Conway said he brought the case "not only for myself but (for) all terminally ill people who believe they should have the right to die."

A previous challenge to Britain's ban on assisted dying was refused in 2014 after the Supreme Court ruled that Parliament should debate the issue before any legal decision.