Paul Vallely: Ai Weiwei is free – but what about the rest?

David Cameron must keep human rights high on the agenda when he meets China's premier

The empty chair spoke eloquently at the ceremony to award last year's Nobel Peace Prize to the Chinese dissident Liu Xiaobo for "his long and non-violent struggle for fundamental human rights in China". He could not be there to receive it because he was in prison, where he had been incarcerated since 2009, merely for demanding political reform and an end to one-party rule in his homeland.

It seemed a good decision at the time. But now – amidst the tightest clampdown in China for two decades – the Nobel committee might be forgiven for wondering whether the strategy has backfired.

That may seem an odd thing to say in a week in which another prominent dissident, the artist Ai Weiwei, has been freed from jail. Yet the Chinese prime minister, Wen Jiabao, arrived in the UK yesterday against a background of repression unmatched since the Chinese army into Tiananmen Square in 1989, shooting dead several hundred unarmed civilians.

It had seemed that, since then, things had rather improved in China. The rapid economic growth produced by its new brand of authoritarian capitalism has catapulted China into the position of the world's second biggest economy. It still has many poor people; average income is just £2,500 a year. But China has produced a growing middle class of professionals and entrepreneurs with annual salaries ten times the national average. That middle class is 300 million strong, and should double by 2025.

Luxury boutiques are no longer confined to Shanghai and Beijing. There is an influential group with values not that dissimilar to middle classes everywhere. Economic change has brought cultural change. Urban citizens have far more choices – in their work, homes and leisure. They can express themselves, publicly and privately, on the streets and in court, in ways unheard of 20 years ago. Public debate on the internet, though far short of Western levels of openness, has been transformed.

So what went wrong? The first tightening came when Chinese security forces began to "tidy" the city in preparation for the 2008 Beijing Olympics and its thousands of international visitors. Among those tidied away was Hu Jia, an Aids activist who concluded that the authorities' lack of respect for Aids patients and orphans was rooted in a disregard of human rights. He was imprisoned for fear he might embarrass the authorities during the Games.

It was pretty minor stuff. Among others arrested were people protesting at being forced from their homes for Games redevelopment. Two elderly women were given "re-education" sentences merely for requesting permission to demonstrate. In the months that followed there was low-level harassment of lawyers who acted for such victims.

But it was with the award of the Nobel prize to Liu Xiaobo last October that things moved up a gear. Beijing reacted angrily, blocking all foreign news broadcasts into China. It pressured foreign diplomats to boycott the Nobel ceremony in Oslo. Nineteen nations capitulated to the blackmail, ensuring that Liu's was not the only empty seat that day. In China hundreds of people – 274 of them named by Amnesty – were arrested, placed under house, refused permission to travel or prevented from going about their daily work.

Yet that Nobel prize hugely boosted morale among Chinese pro-democracy campaigners. So much so, that when country after country in the Arab world rose against their overlords, the dissidents in China began to talk about their own Jasmine Revolution.

In February, just a month before the annual meeting of China's largely ceremonial parliament, the National People's Congress, a page appeared on Facebook under the user name "China's Jasmine Revolution". It urged people to meet at designated places in Beijing and 12 other cities. Only a few hundred people turned up. But their slogans must have unnerved the authorities: "We want food, we want work, we want housing! We want fairness, we want justice! Guarantee property rights, protect judicial independence! Terminate one-party rule! Lift restrictions, free the press! Long live freedom, long live democracy!"

There was a clear similarity between the complaints being voiced by the protesters in the Arab Spring and now in China: growing economic and social inequalities, millions with no access to healthcare, police abuses, suppression of religious freedoms and other human rights. Police cleared the streets and made arrests. So on Day Two the organisers instructed the protesters not to shout slogans but to stage a silent "strolling" protest and to order Set Meal No3 at the local McDonald's and KFC.

The aim was to subvert the Tiananmen Square model of state violence since used in Bahrain and Syria. Beijing responded by blocking the word "jasmine" on internet search engines and Twitter. Police even banned the sale of jasmine blossom at various flower markets, causing wholesale prices to collapse.

Since then, the state has been sending mixed signals. Ai Weiwei has been freed. So has Xu Zerong, a historian jailed in 2001 for "leaking state secrets" – from books about the Korean War. And, last month, the authorities offered an unofficial payoff to a family bereaved in the crackdown that followed the Tiananmen Square protests, though they declined to combine it with an apology.

But those considered serious threats, such as the Nobel laureate Liu Xiaobo – who had in 2008 drawn up a charter demanding gradual political reforms – remain in jail. For Liu, a veteran of the 1989 protests, it was the fourth time he has been jailed.

Even the few activists released in recent months have been gagged. "For intellectuals," said one of the bolder bailed men, the artist Wu Yuren, "here is less and less free space." One director recently had to make 400 changes to his film before the censors passed it.

David Cameron will know, when he meets the Chinese premier tomorrow, that the Beijing regime's consistent message is that China does not respond well to pressure. It has just blocked a multibillion-dollar order for 10 Airbus superjumbo planes in protest against the EU plan to make foreign airlines pay a pollution tax when they fly into Europe from next year. Nearer home, Chinese naval boats have twice cut the cables of Vietnamese oil exploration ships as China expands its claim over the oil and gas-rich South China Sea.

Last time the British raised human rights, the Chinese politicians ping-ponged back a tart inquiry about overcrowding in Britain's prisons, why our age of criminal responsibility is only 10 (it's 14 in China) and our policing of the UK's ethnic minorities. The PM must be ready for that, and more. But he must not recoil from raising, politely but pointedly, our concerns over those political prisoners languishing in China's jails. Ai Weiwei may be free. There are many more who are not, yet ought to be.