Hong Kong has been gripped by 10 weeks of large-scale and occasionally violent pro-democracy demonstrations, which have been met by a sometimes brutal police response, and increasingly trenchant threats from Beijing.

On Monday, two Chinese state media outlets ran video footage showing armoured personnel and troop carriers purportedly driving to Shenzhen, which borders Hong Kong, prompting concerns about military intervention.

Under the so-called “one country, two systems” arrangement that had Hong Kong returned to Chinese rule, Beijing considers the population to be Chinese nationals. However, a number of people in the territory hold what is known as a British national (overseas) passport, which gives some rights, for example to stay in the UK for up to six months, but no automatic ability to live permanently or work.

Tugendhat said: “The UK had obligations to Hong Kong citizens before 1997, and the extension of overseas citizenship, which is in many ways a second-tier citizenship, was a mistake, and I think it’s one that should be corrected. At a time when there are clearly tensions in Hong Kong, the UK could reassure many Hong Kong citizens that their existing rights are recognised by the UK, and they are valued.”

He said this was more about giving reassurance to Hong Kong’s people than facing down Chinese threats.

Tugendhat said: “These are still Chinese citizens from the special autonomous region, so I don’t think the Chinese government would see them as anything other than Chinese citizens under a slightly different status. I don’t think that’s the point.

“I think the point is that the UK has got an opportunity to right a wrong, to give confidence to a people that is clearly very nervous about its future, and understandably so, and I think it’s the right thing to do. And I think all those come together now.”

Hong Kong’s airport, a principal regional hub, had flights suspended for a second consecutive day on Tuesday as protesters rallied there.

Carrie Lam, the territory’s beleaguered chief executive – the head of the autonomous government chosen by a limited electorate stacked with pro-Bejing groups – said on Tuesday that continued unrest would “push Hong Kong down a path of no return, will plunge Hong Kong society into a very worrying and dangerous situation”.

Tugendhat, whose committee said in a report in March that increasing mainland Chinese interference in Hong Kong risked seeing the hands-off approach of one country, two systems, replaced by “one country, one-and-a-half systems”, urged restraint.

He said: “I don’t know what the future looks like. I can’t predict it. But what I can say is that a period of calm would be beneficial to everybody. The only way that this is going to be resolved is by political conversation. It’s not going to be resolved by violence on the streets or anything like that.”