Lord Patten has spoken exclusively to Sky News during a London summit for Hong Kongers who have come to live in the UK due to Beijing's increasingly strong grip on Hong Kong.
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.