Hong Kong on Monday began hearing a Philippine domestic helper's legal bid for permanent residency in the city, in a highly divisive landmark case that has sparked heated debate. Rights activists have said a successful legal challenge will be a first in Asia, and a recognition of rights and equality for domestic workers, who are mainly from labour-exporting nations like the Philippines and Indonesia. The case of Evangeline Banao Vallejos, a Filipina maid who has lived and worked in Hong Kong since 1986, has seen newspapers debate the rights and wrongs of the case for weeks. Several people have been arrested for public order offences after supporters and protesters clashed over the issue. Vallejos launched the legal battle last year after her attempts for permanent residency -- which allows a person to vote and gives them better access to public services -- were denied by the city's immigration authorities. Vallejos' lawyers said in opening arguments that the authorities' refusal to grant her permanent residency was discriminatory and unconstitutional. "There is no criteria (in the constitution) that any group must satisfy certain higher standards," counsel Gladys Li told the High Court, which was packed with journalists, lawyers and activists. "There is no exclusion based on race, religion, nationality... or place of birth," Li added. Under Hong Kong's Basic Law, the city's mini constitution, non-citizens are entitled to permanent residency if they have "ordinarily resided" in the city for a continuous seven years. The immigration laws, however, specifically exclude the 292,000 foreign domestic helpers in the city as they are not considered to be ordinarily resident. The case, which is expected to be heard for two days, has prompted a series of debates, with critics saying that if the court rules in favour, it will open up the floodgates to thousands of foreign maids to apply for residency. The biggest pro-government party warned there would be an influx of as many as 500,000 people -- including children and spouses of foreign maids -- and it would cost an extra HK$25 billion ($3.2 billion) in social welfare spending. The Democratic Alliance for the Betterment and Progress of Hong Kong said any immigration would come at the expense of local workers and forecast unemployment could jump from the current 3.5 percent to 10 percent. The authorities have declined to divulge how many foreign domestic workers will be entitled to permanent residency, if Vallejos' case is upheld.