The last governor of Hong Kong, Lord Patten, has said it is "demeaning and delusional" for the UK to not call out China's behaviour over trade fears.

Lord Patten, who is now chancellor of Oxford University, said China is a threat "we have to engage with in order to deal with global problems like climate change".

He criticised Rishi Sunak after the prime minister appeared to soften his approach to China in November when he said the UK should stand up to Beijing "with robust pragmatism".

"A phrase that belongs to what I call the 'mush' school of diplomacy," Lord Patten said at this week's UK-Hong Kong Summit, which brought together Hong Kongers who have moved to the UK after fleeing their homes.

He said the Chinese Communist Party (CCP) is a threat to the UK's long-term security interests, values and institutions, and that can be seen in how they have treated Hong Kong recently.

But, he told Sky News Hong Kongers should not give up hope because "dictatorships, totalitarianism doesn't last forever".

"When it crumbles, it goes very quickly," he said.

The handover of Hong Kong from the UK to China in 1997, which Lord Patten oversaw, came as part of an agreement that Hong Kong would be self-governing with a high degree of autonomy that would remain unchanged for 50 years.

But in 2014, China stated it considers the treaty to be spent and democracy and autonomy in Hong Kong have since rapidly eroded, with a national security law imposed in 2020 seeing democracy activists and politicians jailed.

Lord Patten said the British government is doing a lot to speak out against Hong Kong.

And he also praised the BNO passport scheme, which has allowed those with a passport issued under British rule the ability to come and live in the UK.

But he said they could be doing more, especially with regards to British citizen and Hong Kong media tycoon Jimmy Lai, who has been jailed for lighting a candle at a Tiananmen Square vigil, among other charges his lawyers say are trumped up.

The government has been accused of being softer on China than it should be because it is concerned about losing trade or not getting a good post-Brexit trade deal with Beijing.

Lord Patten told Sky News: "The CCP pretend you can only do business if you do what they want but look at Australia.

"They were in the doghouse and trade exports from Australia to China have gone up again because China needs barley and the [iron] ore.

"It stopped buying the wine but the wine was sold elsewhere because exports are fungible.

"I think we shouldn't buy this idea that in order to do trade with China we have to do whatever the Communist Party wants.

"We don't behave like this with anybody else - if you want to trade with Nigeria you don't take the view that you can't say anything the president of Nigeria will disagree with.

"So we shouldn't do that with China either. It's demeaning and delusional."

'China wants to retain ability to launder corrupt earnings through HK'

The peer has been highly critical of China in the past few years and said the fact Beijing broke its word over Hong Kong, its promise to not send its military to the South China Sea and about where COVID began shows the CCP - and President Xi Jinping - cannot be trusted.

"The real problem is Hong Kong represented all those things which Xi Jinping and his colleagues were trying to stamp out in the rest of China," he said.

"Stamp out all those things which you identify with Hong Kong while retaining their ability to launder their corrupt earnings through Hong Kong - that remains, cash is king."

'Being in China's doghouse doesn't matter'

Lord Patten last went to Hong Kong in 2016 - "a place I love and hugely admire", he said - but he does not think he could safely return "while the CCP is running it with its quisling administration".

The last governor called on Hong Kongers in the UK to remind the British government of the importance of its moral and political responsibilities to Hong Kong.

He said they should tell their MPs to speak up for people "who are your friends and my friends who are locked up because they believe in the same things as we do" as well as human rights abuses committed by Beijing across China.

"Some people suggest if you mention those things it will so annoy the Chinese communists they'll put you in the doghouse," Lord Patten added.

"If you don't do those things you should be in the doghouse - but the doghouse, as we've seen in relation to this country, Australia, elsewhere, it doesn't actually last for very long and it doesn't matter very much."