Chief Executive John Lee said on Monday the founder of the now-defunct Apple Daily, Jimmy Lai, deserved the 20-year prison sentence handed down on him as the case marks an important milestone in Hong Kong's work in safeguarding national security.

Lai was imprisoned on three counts of conspiracy to collude with foreign forces and printing seditious materials, while eight co-defendants were given jail terms of between six years and three months and 10 years.

Lee said the 156 days of open trial hearings – during which large amounts of evidence were offered – showed that Lai was a despicable and shameless anti-China mastermind.

The CE said in a statement Lai "has committed numerous heinous crimes, and his evil deeds were beyond measure."

"The severe sentence of 20 years' imprisonment imposed on him manifests that the rule of law is upheld and justice is done, and also brings great relief to all," he added.

However, Lee noted that despite the sentencing, Hong Kong had already paid a hefty price.

He said some residents, particularly young people, were misled by Lai's Apple Daily into breaking the law and became radicals during the 2019 "black-clad violence".

Lee said as this was the first collusion conviction under the National Security Law, it marks an important milestone in Hong Kong's efforts to safeguard national security.

He said the SAR would continue to resolutely safeguard the country's sovereignty, security as well as developmental interests.

A government spokesman stressed that the fair trial had demonstrated that malicious accusations and slander from western countries and anti-China media outlets overseas would not stand up to scrutiny.

He said they, along with numerous organisations and politicians, had persistently smeared Hong Kong's efforts in upholding national security.

"These countries themselves frequently deploy the tactics of overstretching the concept of national security as a pretext to suppress their own opponents.

"Moreover, they have been harbouring their agents by constantly slandering Hong Kong, hypocritically cloaking Lai Chee-ying in the false guise of a 'media mogul', and even fabricating health problems of Lai Chee-ying during the trial."

In accordance with the law, he said, the Correctional Services Department has always ensured that detention conditions are safe, healthy, humane and appropriate.