By Venus Wu

HONG KONG (Reuters) - A Hong Kong court on Tuesday disqualified two pro-independence lawmakers from taking office, ruling their oath of allegiance invalid in a judgment in step with Beijing, which last week intervened in the Chinese-ruled city's legal system.

But High Court Judge Thomas Au said he would have made the ruling anyway, without the controversial "interpretation" by China's parliament that some lawyers and activists warned had damaged the judicial independence of the global financial hub.

Au acknowledged the decision by the National People's Congress was binding, but he did question whether the move fell within the legal scope of an interpretation under the Basic Law, the mini-constitution that governs Hong Kong's relations with Beijing.

The congress ruled that Hong Kong legislators must solemnly swear allegiance to Hong Kong as part of China, adding that candidates who take the oath of office in an insincere manner will be disqualified and not given another chance to swear in.

Democratically elected legislators Yau Wai-ching, 25, and Baggio Leung, 30, sparked controversy when they displayed a banner declaring "Hong Kong is not China" and substituted derogatory terms for "China" while taking their oaths last month.

Au placed an injunction on the two acting as legislators, as well as on Legislative Council president Andrew Leung from re-administering any new oath for the pair.

"With or without the interpretation (by Beijing), the court would reach the same conclusion," Au said in the summary of the 56-page judgment.

"By seeking to make a mockery of China...in a derogatory and humiliating manner, it is objectively plain that Mr Leung and Ms Yau refused to pledge allegiance to the Hong Kong Special Administrative Region as an inalienable part of (China)," he said.

The pair told reporters they made the "heavy" decision to appeal, even though they might end up bankrupt.

Hong Kong, a former British colony, returned to China in 1997 under a "one country, two systems" agreement that ensured its freedoms and wide-ranging autonomy, including a separate legal system.

But Communist Party rulers in Beijing have ultimate control, stepping in to interpret the Basic Law, and some Hong Kong people are concerned they are increasingly interfering to head off dissent.

The way the pair took the oath demonstrated "objectively and clearly their intention not to recognize this fundamental constitutional model of 'one country, two systems' and the importance of ... 'one country'," Au's judgment said.

Beijing's interpretation represents some of the worst privately held fears of senior judges and some government officials in Hong Kong, according to sources close to them.

Demonstrators angry at Beijing clashed with riot police last week, unfurling umbrellas to block pepper spray in scenes reminiscent of the 2014 pro-democracy protests, dubbed the "Umbrella Movement", that brought key intersections to a halt for weeks on end.

About 2,000 members of Hong Kong's legal community marched in silence later in the week to protest against what they called a "severe blow" to the city's judicial independence.

Yau appeared calm at the High Court as her lawyers went through the judgment with her. She said she found the decision unfair.

"I think the government used so many ways to give pressure to the court. Under such pressure, it is expected that the court may make such a judgment," Yau said.

Chief Executive Leung Chun-ying, who filed the lawsuit along with the city's Secretary of Justice in the first place, told reporters he welcomed the court ruling and the government was looking into follow-up actions. He did not elaborate.

Legislature head Andrew Leung said he accepted the court's decision.

Tens of thousands of government supporters over the weekend rallied against the promotion of Hong Kong independence, a topic once taboo but becoming increasingly mainstream since the 2014 street protests failed to stop Beijing from vetting candidates for the city's leadership elections.

Chinese officials in public and private comments have said talk of separatism, including advocacy for self-determination, is not to be tolerated.

A senior official in Beijing's representative office in the city said last week that up to 15 members of the Legislative Council had given insincere oaths - raising the prospect of a wider purge of radical voices.

Apart from the Leung and Yau, at least four lawmakers in the 70-member council support various degrees of greater autonomy for Hong Kong.

They collectively received one in five votes in September's city-wide election, though the pair's popularity has dropped since the oath-taking controversy.

(Reporting By Venus Wu and Stefanie McIntyre,; Editing by Nick Macfie and Greg Torode)