Proposed amendments to the Legal Practitioners Ordinance would not be retroactive, Secretary for Justice Paul Lam said on Friday, adding that the changes would not mean a blanket ban on overseas lawyers taking on national security cases.

Authorities put forward changes to the ordinance after the country's top legislature passed an interpretation of the national security law late last year, stating that courts need approval from the chief executive to allow foreign lawyers without full qualifications to practise in Hong Kong to take part in national security cases.

Under the proposals, applicants would have to obtain a notice of permission by providing relevant information and supporting evidence, before they could file a formal application to take part in a national security case.

The government also suggests allowing the courts or the Secretary for Justice to request a new approval from the chief executive if there are circumstances warranting a review on a granted permission.

"The new proposal will only apply to cases after the legislative amendments. It will not cover cases where ad hoc admission has been granted," the justice secretary told lawmakers.

"We are talking about a brand new system. Our review mechanism will not apply to applications lodged or dealt with by the courts before the legislative amendments. Such cases will not be covered."

Legal sector lawmaker Ambrose Lam said there should be a blanket ban on foreign lawyers.

"The national security law is drafted in Chinese, there is no official English version," he said. "Does the secretary for justice agree that overseas counsels are not suitable for acting as barristers in national security cases?"

The justice secretary disagrees that only those proficient in Chinese should take on national security cases.

"We have important cases where lawyers and even judges not proficient in Chinese took part, and the judges wrote the judgements. They contributed to our jurisprudence, and also helped people overseas not proficient in Chinese get a proper understanding of our national security law," he said.

Paul Lam added that a case-by-case approach is more in line with the interpretation made by the National People's Congress Standing Committee, and will allow for more flexibility.