Sir Keir Starmer is on his way to Beijing, making the first trip to China by a British prime minister since 2018.
He is due to meet President Xi Jinping on Thursday.
Around 60 British business and cultural leaders are also on the trip, including representatives from bank HSBC, pharmaceutical company GSK, Jaguar Land Rover and the National Theatre.
It marks the latest and most important moment in the government's attempt to reboot the UK's relationship with China. But critics argue China is of a wildly different world view, can't be trusted and the government ought to be much more cautious in its dealings with its Communist Party.
When asked if the prime minister would raise human rights abuses with the president, Downing Street said he would "raise challenging issues where interests and values differ".
