Chinese official pronouncements have been cautious. President Xi Jinping reportedly indicated to Cameron during a state visit to the UK in October that China would prefer Britain to remain in the EU. This was later backed up by a Foreign Ministry statement.

During Xi's visit, deals worth 40 billion pounds ($58.73 billion) were announced with Chinese companies.

US President Barack Obama says he would prefer the UK to remain in the EU, as would major European players such as France and Germany.

Li Ka-shing, one of the richest men in Asia, told Bloomberg Television on Tuesday he was urging Britons to vote to remain, because a decision to leave would cause "great damage to the country and the EU".

He said a vote to leave would not be the end of the world, but as a major investor in the UK, he would continue to maintain his business interests in the country, as well as Europe in general.

Bloomberg reported earlier remarks by Li, in which he said he did not believe Britain would vote to leave, but if it did, he would consider reducing his investment there.

Li has a fortune of $28.6 billion, according to both Forbes and the Bloomberg Billionaires List, making him the third-richest man in Asia.

Many Chinese companies operating in the UK see the country as a bridgehead into Europe, a function that would suffer in the event of a vote to leave the EU.

This view is supported by Yao Lin, deputy director of a research center supervised by China's Ministry of Commerce.

Yao warned in a paper that many Chinese companies investing in Britain as a way into the EU single market would see the "bridgehead curtailed'' in the event of a vote to leave.