An angry open letter urging Chinese Australians to "take down the far-right Liberal Party ruling party" by voting against John Alexander in the Bennelong byelection has been shared on social media by a man who allegedly met the Chinese Communist Party's department tasked with overseas influence activities.

The 1700-word letter, attributed to "a group of Chinese who call Australia home", urged people to support Labor's candidate, Kristina Keneally.

"When we look at the Liberal Party we see it's already totally different from before. It's a far-right ruling party and they are privately against China, against Chinese, against ethnic-Chinese migrants and against Chinese international students," it reads in part.

"For the interests of Chinese people, let us mobilise, share this message and use the ballots in the hands of we Chinese to take down this far-right Liberal Party ruling party".