Former media tycoon Jimmy Lai has filed a legal challenge against the government’s decision not to issue a work visa so that British barrister Timothy Owen can represent him in a national security trial.

In a writ filed to the High Court, Lai also asks the court to revoke a decision by the Committee for Safeguarding National Security that allowing Owen to take part in the trial would pose a risk to national security and China's interests.

Lai, founder of the now-defunct Apple Daily newspaper, is accused of taking part in a conspiracy to print, publish, sell, offer for sale, distribute, display and/or reproduce seditious publications, as well as conspiring with others to collude with a foreign country or external elements to endanger national security.

His trial is due to get underway on September 25.

The Court of Final Appeal had ruled in favour of Lai’s application to engage Owen, but Chief Executive John Lee subsequently asked the National People’s Congress Standing Committee (NPCSC) for an interpretation of the national security law regarding overseas lawyers’ participation in such cases.

The NPCSC ruled last December that the courts need the chief executive’s approval for foreign lawyers to take part in sensitive security cases.

Lai earlier also filed another writ, contending that the NPCSC decision does not affect his trial.

In an affidavit filed to the court in response, the director of immigration disclosed that he was advised by the security committee in January this year that Owen’s visa application should be refused.

Following this disclosure, Lai mounted another challenge – against the mandate of the security committee. He said that if the committee is empowered to decide whether any judicial procedure is related to national security, the entire judicial system will collapse given the fact that the committee is not subject to any judicial reviews.

No hearing date has been set for any of these writs yet.