The man who launched a legal challenge to the government's attempt to invalidate 20,000 vaccine exemption certificates said on Friday he was appealing against a decision to deny him legal aid in the case.

Kwok Cheuk-kin, known as the "king of judicial reviews" because of his frequent legal challenges, will be back in the High Court on Thursday for a full hearing after Justice Russell Coleman this week granted an interim relief order blocking the cancellation of certificates issued by seven doctors suspected of giving out the papers improperly.

However the Legal Aid Department earlier blocked Kwok's application for public funds in the case on the grounds that he is not directly affected because he has received three doses of the Covid vaccine.

Speaking to reporters on Friday, Kwok said he should receive legal aid as the case involves public interest. He noted that he had received legal aid for an earlier challenge to the small house policy, under which male indigenous villagers are allowed to build homes on private or public land, despite not being directly affected.

Kwok also revealed that a woman who holds an exemption certificate may join him in his legal fight. However, he pointed out that the woman's waiver was not issued by one of the seven doctors whose certificates are earmarked for cancellation.

The certificates allow people who are not fully vaccinated to enter premises such as restaurants. Government lawyers argue that the invalidation is justified on public health grounds and say that people affected can visit another doctor, including free public doctors, to seek a new exemption certificate.

The government had said it would cancel the vaccination certificates on Wednesday this week, but has held off since Justice Coleman issued his relief order on Tuesday.