Sydney - Australia's conservative government vowed on Thursday to pursue efforts to tighten the country's citizenship requirements after parliament refused to approve the crackdown.Prime Minister Malcolm Turnbull proposed the tougher rules in April, adding stringent English-language tests and a quadrupling of the residency requirement for citizenship applicants from one to four years.The move came against a background of growing populist pressure in Australia and a resurgence of the anti-immigration One Nation party led by Pauline Hanson. But the opposition Labor Party and other critics blocked the legislation in the upper house Senate, where a deadline for adoption passed on Wednesday.Criticism of the bill focused mainly on the requirement that new citizens would need to show university-level English proficiency - something Labour said amounted to a "White Australia" policy by discriminating against immigrants from non-English-speaking nations.Opponents also chided Turnbull for describing the new law as putting "Australian values" at the heart of the citizenship process. Immigration Minister Peter Dutton shrugged off the setback in the Senate, where the government needs the support of minor parties to pass legislation, and vowed to reintroduce an amended bill that would slightly ease the English-language requirements.Criminal elementsHe also offered to push back application of the new Citizenship Act until July 2018, rather than make it retroactive to the date of Turnbull's initial announcement in April.But the government stood firm on the four-year residency requirement, saying it was necessary to weed out criminal elements before they became citizens."We're saying that we want people to abide by Australian laws, we want people to adopt Australian values, we want them to work if they're of working age," Dutton said in a radio interview on Thursday."We don't want people coming here just to come on the welfare system."We aren't going to allow the ghettoes that we might see in other parts of the world, where people try and adopt a different legal system or try and shun the English language. We are not going to tolerate that in our country."More than 114 100 people sat the Australian citizenship test in 2014-15, with 112 474 passing it, according to the latest immigration figures.