David Cameron has complained to his Chinese counterparts about their treatment of GlaxoSmithKline, the U.K. drugs company that has found itself caught in the center of a storm over allegations it bribed Chinese doctors to sell its medicines.
The prime minister raised the issue during meetings with China's top politicians in Beijing on the first day of a three-day trade mission to the country.
(Read more: GSK's China sales topple on bribery scandal)
A Number 10 official said: "The prime minister discussed British business interests in China and the need for them to think China is a secure and stable environment for them to operate in."
GSK's medicine and vaccine sales in China have dropped 61 percent since the summer, following the high-profile corruption probe launched by Beijing into the pharmaceutical company's alleged business practices.
Sir Andrew Witty, GSK chief executive, is among a 127-strong business delegation travelling with Mr Cameron on a trip intended to boost U.K. economic ties with China and draw a line under a period of diplomatic tensions between the countries.
After talks with Premier Li Keqiang, Mr Cameron trumpeted Britain's openness to Chinese investment and vowed to lead the push for an EU-China trade deal.
"Some in Europe and elsewhere see the world changing and want to shut China off behind a bamboo curtain of trade barriers. Britain wants to tear those trade barriers down."
Premier Li used a joint news conference in Beijing to raise the possibility of Chinese investment in the U.K.'s plan for a £50 billion high-speed rail line from London to the north of England, in addition to existing plans to invest in U.K. nuclear power.
"The two sides have agreed to push for a breakthrough and progress in co-operation in the areas of nuclear power and high speed railway," said Mr Li.
"Just like high speed trains, we need to grow this relationship at a faster speed."
The form of any Chinese investment in HS2 is as yet unclear, but British officials stressed there would be no direct investment in the construction phase of the line, which is due to be funded by the taxpayer. This leaves open the possibility of the Chinese bidding for the concession to run HS2 or investing in peripheral schemes around the route such as developments around stations when the route opens in the 2030s.
The move could prove controversial, deepening Chinese ownership of British infrastructure projects. The UK's first nuclear power station to be built in a generation was agreed to last month, with the backing of EDF, the French energy company, and various Chinese investors.
The visit is his first to China since November 2010, and the first since the current regime took over in November 2012. British ministers had until recently been refused meetings with their Chinese counterparts after the prime minister met the Dalai Lama in London in May 2012.
Mr Cameron has made trade the focus of his trip, despite concerns over human rights violations in China. He said the British government wanted to support "the judicial protection of human rights", but made it clear that discussions between the two countries over the issue would be held separately next year.
The prime minister insisted that his government should not be embarrassed about its increasing reliance on Chinese capital. Speaking to journalists, the prime minister said: "I'm not embarrassed that China is investing in British nuclear power, or has shares in Heathrow airport, or Thames Water, or Manchester airport. I think it's a positive sign of economic strength that we are open and welcome to Chinese investment."
(Read more: China plenum to 'surprise' on reforms: Stephen Roach)
A raft of new healthcare deals were among the contracts highlighted by Mr Cameron on Monday, including a Chinese joint-venture with U.K.-based Heythorp Healthcare to provide elderly nursing and specialist dementia care in the country.
The government has targeted the health market among its priority opportunities in China as ministers seek to export expertise from the National Health Service.
Jeremy Hunt, health secretary, who has accompanied Mr Cameron on the trip, highlighted both countries' "similar challenges" in caring for an ageing population and said U.K. companies had "much to offer in the Chinese elderly care market".