Ai Weiwei urges David Cameron to challenge Beijing as the PM leads the largest ever British delegation to China

China's best-known artist, Ai Weiwei, has urged David Cameron to press Beijing on human rights issues this week, as the prime minister leads the largest-ever British delegation to the country.

Writing in the Guardian on the eve of Cameron's visit, Ai says that there has been a pitiful change in global attitudes to China since the economic crisis, with western leaders increasingly reluctant to challenge Beijing.

"Cameron should ask the Chinese government not to make people 'disappear' or to jail them merely because they have different opinions … Cameron should say that the civilised world cannot see China as a civilised country if it doesn't change its own behaviour," he writes.

It is understood that the prime minister plans to raise the case of Nobel peace prize winner Liu Xiaobo, serving an 11-year sentence for co-writing a call for democratic reforms. Four weeks ago, he was awarded the Nobel Peace Prize for his human rights activism, a decision that incensed the Chinese government, which regards him as a criminal.

While it is very rare for people to disappear in China, there has been international concern over human rights lawyer Gao Zhisheng, who has not been seen for months.

Ai, creator of the "sunflower seeds" installation currently in the Turbine Hall of Tate Modern , was himself due to be released from house arrest at midnight last night. Police restricted his movements last week after thousands of people accepted his invitation to a party at his condemned studio in Shanghai.

In his first official visit to China, Cameron will hold a summit tomorrow with the Chinese premier, Wen Jiabao and President Hu Jintao, at which he is expected to focus on improving trade, but will also mention human rights issues.

The five-day tour of the far east and it will culminate in a potentially tense showdown at the G20 summit in Korea.

The scale of the visit beats Cameron's trip to India, an event that led to Downing Street feeling pressurised by the Chinese to field an equivalent size or larger delegation. Cameron will be accompanied by the chancellor, George Osborne, education secretary Michael Gove, the business secretary Vince Cable and the energy secretary Chris Huhne.

Fifty business leaders, from companies ranging from Tesco to Rolls Royce will accompany Cameron, and also attend a China-UK Business summit with Chinese leaders. This makes it even bigger than the business delegation who went to India.

William Hague, the foreign secretary, told the cabinet on Tuesday that China was expected to build 86 airports in the next five years, a small indication of growth and the business opportunities available.In a sign of what a bilateral deal is worth, Hu signed contracts worth £8.6bn with the French during a state visit last week, covering 102 Airbus planes, as well a the telecoms and nuclear sectors.

British officials point out that China is still a controlled economy and even in the case of private sector investment the umbrella of state officials are needed to get the go ahead to invest.

The Chinese have warned the British not to raise human rights issues, but neither side intends to let the issue dominate what is supposed to be a visit focused on raising exports.

Cameron may come under pressure from the Chinese to condemn the US Federal's reserve decision last Wednesday to buy $600bn worth of government bonds, in the hope that the cash injection can kickstart the US economy.

The move weakens the dollar, making imports from China, a major trading partner, more expensive for US consumers.

"If the domestic policy is optimal policy for the United States alone, but at the same time it is not an optimal policy for the world, it may bring a lot of negative impact to the world," said China's Central Bank head Zhou Xiaochuan.

Cui Tiankai, China's vice foreign minister, said the Federal Reserve had the right to take steps without consulting other countries beforehand, but added: "They owe us some explanation."China has been under pressure to appreciate its currency against the dollar in order to let in more imports.

British officials are playing down any great breakthrough on the issue of currency wars between China and the US at the G20 summit to be held in Korea on Thursday and Friday. "It is more a case of managing the process", said one official.

The officials also said the G20 was moving away from big dollar announcements designed to help the world's poor. The Koreans have been urging the G20 to look at an alternative approach based on approaches such as trade, investment and studying how other emerging economies - such as their own – have grown rapidly.

The same officials, determined to lower expectations, also said they saw no prospect of a breakthrough over climate change saying the issue has been deferred to Cancun conference in a month's time.

Chris Huhne is due to sign a number of bilateral deals on renewable energy technologies with China, the country most likely to add to global pollution as its industrialisation grows apace. Some blame China for the failure to agree a legally binding deal at Copenhagen.

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In probably his main G20 initiative, Cameron is likely to press the case for a new world trade deal, arguing the room for manouvre around fiscal and monetary policy is becoming increasingly limited leaving trade as the best way to boost world demand.

With Obama facing Presidential elections in two years, British officials see the next 12 months as the critical window of opportunity to secure a trade breathrough. The time left is very limited warned one official, adding " this is the best boost we can give to the world economy at a time when we are running out of fiscal and monetary flexibility".