HONG KONG, July 27, 2010 (AFP) - Hong Kong activists will rally on Sunday against China's bid to champion its national language Mandarin over Cantonese, following a rare protest for the same cause in southern China.

Organisers have called on supporters via Facebook to help protect their mother tongue, after hundreds protested in support of Cantonese in the city of Guangzhou last weekend, defying government orders.

The demonstrations follow official advice issued to southern Chinese TV stations proposing they switch key shows into Mandarin from Cantonese.

Choi Suk-fong, one of the organisers of the Hong Kong protest, said Beijing's moves to promote Mandarin were a form of suppression of the rights of minorities in the country.

"Cantonese was often portrayed as a second-class language when Hong Kong was under British colonial rule," she told AFP.

"Sadly, the use of our mother tongue is now being attacked again, only that this time the perpetrator is our Chinese government."

The People's Political Consultative Conference -- a political advisory body in Guangzhou -- wrote this month to the province's bureaucrats proposing that local TV stations broadcast their prime-time shows in Mandarin instead of Cantonese ahead of the Asian Games in November.

Adopting China's official language, also known as Putonghua, would promote unity, "forge a good language environment" and cater to non-Cantonese-speaking Chinese visitors at the huge sporting event, authorities were quoted as saying.

The organisers wrote on the Sunday event's Facebook page: "I believe we can gather 100,000 people to stop China's evil act of promoting Mandarin and destroying Cantonese!!!"

More than 150 visitors to the Facebook page had signed up for the protest by Tuesday afternoon, including some from Guangzhou, where the original protest was held last Sunday.

Many of the demonstrators there were young people wearing T-shirts reading "I love Guangzhou" written in Cantonese, and shouting "Protect Cantonese, Love Guangzhou" and singing popular Cantonese songs, the Global Times reported.

Instances of mainland protests spilling over into Hong Kong, which was returned to China in 1997, are rare since China's 1989 Tiananmen crackdown on pro-democracy demonstrators.

Su Zhijia, a deputy Party secretary of Guangzhou, was quoted as saying there were no plans to dilute Cantonese.

"The city government has never had such a plan to abandon or weaken Cantonese," he said according to the state-run Global Times.

Guangzhou TV has responded by saying it would refuse to change its mix of Cantonese and Mandarin programming, The Yangcheng Evening News said last week.

But many Cantonese speakers still worry about the future of a language that is the mother tongue for people in Hong Kong, Macau and China's southern Guangdong province, and is widely spoken in overseas Chinese communities.

China has long been a patchwork of often mutually unintelligible dialects, but Mandarin -- which is based on the traditional dialect of Beijing -- became the lingua franca of the nation beginning with the Qing dynasty (1644-1911).

Beijing made Mandarin the country's official language in 1982, leading to bans on other dialects at many radio and television stations.

Mandarin's strength has increased since the 1949 Communist takeover as authorities sought to promote its use as a unifying force for the nation.

It has been further promoted in recent years as migrant workers who speak their own dialects moved to China's coastal areas to find jobs.

That has caused disquiet in areas with their own strong language traditions, such as Tibet, Xinjiang, Inner Mongolia and Guangdong.