Former UK chancellor of the exchequer Kenneth Clarke said Britain could only hope for an unequal treaty with China if it leaves the European Union.

One of the central arguments of those arguing for a Brexit vote in the referendum on June 23 has been that the UK would be able to strike better trade deals with the world's second-largest economy as well as the United States and India.

"The idea of the British sitting down and negotiating a trade deal with a quite particular government like that of the People's Republic of China is, I think, fanciful. I think the respective weight of the two sides would be quite uneven," he said.

"The complexities involved in negotiating and the kind of understanding we would need to have would make it quite difficult to achieve. I think these things are much better tackled on the scale of an EU agreement."

Clarke, who was speaking in his office in Portcullis House in Westminster, has had a long involvement with China and was the UK's envoy at the 70th anniversary commemoration of the end of World War II in September in Beijing.

He is also one of the most high-profile pro-European figures in the Conservative Party, now deeply divided over the referendum.

"I think the Brexit campaigners have no understanding of how trade is organized in the modern world. Trade deals tend to be extremely complex and involve long negotiations in which you address the problem of tariffs but much more importantly mutual recognition of regulatory and other requirements."

The 75-year-old also does not believe the issue of the UK's membership should have been put to a referendum in the first place.

"I strongly believe in parliamentary democracy. You elect people who are going to be responsible for the governance of the country. The idea of putting enormous all-embracing questions of this kind to an opinion poll and saying that all the politicians should be instructed to follow whatever the poll on a certain day said is, I think, a very curious way of governing a modern and sophisticated country."

He said he will be relieved if voters do, after all, deliver a remain verdict in the poll.

"I will have a great sigh of relief if we vote to remain because the short-term consequences will be quite unpleasant. I can not tell you how severe but if the currency collapsed you would have a significant increase in interest rates."

He also insists it will not be straightforward for a government to implement a leave vote, given the overwhelming majority within parliament for Britain remaining.

"Any government that implements a leave vote will actually be a minority government in parliament so far as actual political principles and beliefs are concerned. They are hoping that enough MPs will have committed themselves to vote regardless of their own beliefs and principles and to vote, as instructed, by the referendum."

Clarke, who came to prominence as a cabinet minister in Margaret Thatcher's administrations of the 1980s, went on to be Home Secretary and chancellor of the exchequer under her successor, John Major.

He held the positions of both justice secretary and minister without portfolio in David Cameron's coalition government before finally leaving office in 2014.

He has been MP for Rushcliffe in Nottingham since 1970 and he revealed that he will be stepping down at the next general election, due to be held in 2020, after by then spending 50 years in the Commons.

"I have told the officers of my constituency association that once we have finished the boundary changes they had better start choosing my successor. I will not stand again. This is my last parliament."

Clarke made his first visit to China shortly after the "cultural revolution" (1966-76) and has been a regular visitor ever since.

"It has been completely transformed as a country. It is obviously the most powerful, emerging country in the world. Its political system is dramatically different from our own and as a lifelong politician, I just find it fascinating and intriguing."

Apart from his attendance at the 70th anniversary commemoration, he led a UK healthcare trade mission to China in 2014 and a parliamentary delegation to the 8th annual UK-China Leadership Forum in Beijing and Shanghai late last year.

"China is going to invest huge sums of money in developing its healthcare systems and I think British expertise in healthcare is of very high quality.

"I think we could be of great value to the Chinese from the design and build and operation of hospitals to the establishment of community healthcare."

Clarke also recently intervened in the debate as to whether to impose tariffs on imported Chinese steel to save Port Talbot steelworks in South Wales, which is threatened with closure.

"I pointed out to some of the more left-wing advocates of simple solutions to save Port Talbot — that you cannot really say you are going to put huge tariffs against the Chinese, nationalize the steelworks and dump our products on the rest of the world using tax payers' money to allow them to sell at less than the cost of production."

He believes that President Xi Jinping's visit to the UK last October was an important staging post in building solid Sino-UK relations that were often mired in the past over issues relating to Hong Kong.

"I did the eulogy at the funeral of Geoffrey Howe (the UK foreign secretary who negotiated the 1984 Joint Declaration) and I thought his handling of the negotiations over Hong Kong were one of the high points of his career, although under appreciated.

"I think we should endeavor at being on the best possible terms with the People's Republic. The more we get to know each other, the more we get slightly economically interdependent and the greater the prospects of my children and grandchildren maintaining a good and friendly relationship."

The former chancellor has even had time on a recent trip to China to indulge his passion for birdwatching.

"We drove to the mountains northwest of Beijing and came across a group of Chinese carrying a fantastic amount of photographic equipment. They were looking at a wallcreeper and we strolled over and joined them. It sounds a dull bird but it is very beautiful, very brightly colored and it clings to rocks. It is quite hard to find."

Clarke is now writing his memoirs, which are due to be published in the autumn. He has been the subject of two previous biographies.

"They were both published when I was standing for the leadership (of the Conservative Party) in 1997. I have not read either but I am told they are perfectly friendly so I might do so now to jog my memory," he said, laughing.

"I am doing my memoirs with a modern dictaphone, which you plug in and it types what you say. I have a couple of young women who are bullying me and editing it and sorting it all out."

The outcome of the referendum may provide the material for the final chapter.

"Everybody would have to be on their toes if we decide to leave. I am sure it will make this country a much less attractive place for investment from China and elsewhere in the longer term."

Contact the writer at andrewmoody@chinadaily.com.cn