BEIJING (AFP) - The French and German ambassadors to Beijing have granted a human rights award to a detained Chinese lawyer, with his wife picking up the prize on his behalf.

Mr Yu Wensheng - best known for suing the Beijing government over the city's once chronic pollution - was detained in January last year and charged with "inciting subversion of state power".

Beijing has stepped up its crackdown on civil society since President Xi Jinping took power in 2012, tightening restrictions on freedom of speech and detaining hundreds of activists and lawyers.

Prior to his arrest, Mr Yu had circulated an open letter calling for five reforms to China's Constitution, including the institution of multi-candidate presidential elections.

His wife, Madam Xu Yan, received the award at an event organised by the German embassy in Beijing on Monday (Jan 14).

The prominent attorney was among 15 winners of the Franco-German Prize for Human Rights and the Rule of Law for 2018, announced in November last year.

"He (Yu) has lost his freedom for a year and not allowed to meet with a defence lawyer," Madam Xu said at the event attended by the German and French ambassadors to China, according to a transcript she posted on her WeChat social media account.

"His case has been postponed three times, and referred back to the police for further investigations twice," Madam Xu told AFP, adding that her husband's case had been referred again for "for review and prosecution" in December.

"I learnt about this situation when I went to the Xuzhou City Procuratorate on Dec 24. I didn't receive any news before that," she said.

"No matter how difficult it is, I will continue to defend the rights of Yu Wensheng, because I believe Yu Wensheng," Madam Xu said.

For several days beginning on July 9, 2015, more than 200 Chinese human rights lawyers and activists were detained or questioned in a police sweep that rights groups called "unprecedented".

The "709 crackdown", as it was later dubbed, marked the largest clampdown on the legal profession in China's recent history.

But Mr Yu was not arrested during the sweep and had continued to express his opinions on legal issues.

German Chancellor Angela Merkel met Madam Xu and Madam Li Wenzu - the wife of another detained rights lawyer, Mr Wang Quanzhang - during her trip to Beijing in May last year, in a rare move for a visiting leader.