LONDON -- Britain will be China's "partner of choice" in the West, Prime Minister David Cameron declared Wednesday, as China demonstrated its commitment by putting down a 6 billion-pound (US$9.3 billion) stake in the U.K.'s first nuclear power plant since the 1980s.

Chinese President Xi Jinping signed the nuclear agreement on the second day of a four-day visit that has seen the two countries agree more than 30 billion pounds ($46 billion) in business deals.

Cameron said the "historic agreement" would create 25,000 jobs and eventually provide power to 6 million homes. But the nuclear deal is a focal point for critics who accuse Cameron of wooing the Chinese for trade deals while ignoring the country's human rights record.

At a joint news conference at 10 Downing St., Xi said China "attaches great importance to the protection of human rights."

"Looking around the world, there is always room for improvement," he said.

Cameron said a strong economic relationship could withstand frank disagreements on some other issues.

"The stronger the relationship between our countries, the more we'll be able to have a serious dialogue," Cameron said. "We may not always agree, but we can discuss issues openly and constructively."

The nuclear deal will see the new Hinckley Point plant in southwest England built jointly by Electricite de France and China's state-owned China General Nuclear Power Corporation.

EDF said Wednesday that it would take a 66.5 per cent share in the 18 billion-pound ($28 billion) plant and CGN 33.5 per cent. The two firms also agreed to develop two further nuclear power stations in southeast England -- one of which would be Chinese-designed and majority Chinese-owned.

The deal must be approved by both companies' boards. EDF said it anticipated a "final investment decision" within weeks.

Some in Britain worry about letting an undemocratic emerging superpower with powerful espionage capabilities access to Britain's critical infrastructure.

"It won't be the physical security that matters, but the cybersecurity," said Alan Woodward, visiting professor of computing at the University of Surrey. "We don't want a foreign power being able to quite literally turn off the lights from some remote location."

Others questioned the economics of the nuclear agreement. The British government agreed to underwrite 2 billion pounds ($3.1 billion) in Chinese financing to secure the deal and has guaranteed the plant's owners a minimum power price for 35 years.

Xi has been welcomed with lavish ceremony on his visit, which began Tuesday with a day of pomp that included an address to Parliament by Xi and a banquet at Buckingham Palace during which Kate, the Duchess of Cambridge, toasted the Chinese leader.

Kate and her husband Prince William accompanied Xi again Wednesday at an event celebrating Britain's creative and technology industries. Xi viewed innovative examples of U.K.-Chinese collaboration, including low-emission versions of a London black cab, a red London bus and James Bond's favoured Aston Martin car -- all due to be developed through deals between the two countries. He also met some members of the team behind hit British TV exports "Sherlock" and "Poldark," and action star Jackie Chan.

Not everyone in Britain has welcomed the government's charm offensive toward China. Xi's visit has drawn protests from human rights and pro-Tibet groups -- though they have been outnumbered by Chinese flag-waving pro-Xi crowds.

Steve Hilton, a former close adviser to Cameron, called the visit "one of the worst national humiliations we've seen."

"I think that we have to be much tougher," he told the BBC. "I think that we should consider sanctions on China, not rolling out the red carpet."

Opposition politicians and trade unionists also have urged Cameron to stand up to Xi over what they see as unfair Chinese commercial competition.

U.K.-based steelmakers have announced several thousand layoffs in recent weeks, blaming China for selling steel at a loss on world markets to secure its own market share.

Challenged in the House of Commons to do more to support British steel, Cameron said the industry was in "a very difficult situation" because of oversupply and a collapse in world steel prices. He said Britain would take action on several fronts, including "unfair competition and dumping."

At the news conference with Cameron, Xi said "the world is facing the overcapacity of iron and steel, not just the U.K." He said China had cut back on its own steel production.

Chinese Foreign Ministry spokeswoman Hua Chunying told reporters in Beijing that "some disagreements or frictions" between economic partners were inevitable.

"The most important part is that both countries agree to properly handle these disagreements and frictions through discussion on the basis of equality and mutual benefit," she said.

Associated Press news assistant Dong Tongjian in Beijing contributed to this report