One of the largest sperm banks in Beijing has set loyalty to the Communist Party as a prerequisite for donors, in a sign that Chinas increasing emphasis on ideological training is being extended to the womb.

As well as being free of genetic or infectious diseases, potential donors must have "sound ideological qualities", according to a notice posted on the hospital's official account on popular messaging app WeChat.

Men between the ages of 20 to 45 who wish to donate semen must "love the socialist motherland, support the leadership of the Communist Party, be loyal to the party's cause and be decent, law-abiding citizens, free of political problems", according to the statement that was deleted from the social media channel on Friday evening.

Those who successfully donate after undergoing two rounds of medical checks -- to assess the quality of their semen and general fitness -- will be paid 5,500 yuan ($900), the statement said.

There were no details on how the hospital would verify whether donors satisfied the political requirements.

AFP's calls to the hospital to ask if these requirements were part of a larger government policy went unanswered.

China has only 23 sperm banks nationwide, according to the country's National Health Commission, and many have long been plagued by a severe shortage of donors.

Requirements for donors at other major collection centres, including others in Beijing and those in Shanghai and Guangzhou, do not include loyalty to the party.

The controversial campaign, which runs until late May, has inspired several tongue-in-cheek comments by Chinese internet users.

"Love for the party starts with a sperm," wrote one social media commentator on WeChat.

"Maybe they haven't learned biology. Acquired traits can't be passed down," wrote another on microblogging service Weibo.

The Communist Party's membership comprises 6.5 percent of China's population of almost 1.4 billion people.