Lawmakers criticised the Immigration Department yesterday for trying to track down a 'whistleblower' who disclosed that deputy minister Greg So Kam-leung had given his business card as proof of income in a contract application for his maid. They said the department's actions would frighten off civil servants from exposing illegal or unjust activities in the public interest. A civil service union agreed, saying the informer had been 'courageous'. But the department union said it supported the investigation into how the action by Mr So, undersecretary for commerce and economic development, was leaked to the media. A department spokesman said yesterday it was conducting an internal preliminary investigation into any leak of personal data which would breach guidelines designed to protect the privacy of users of the department's services. A department source said three officers had been ordered to submit memorandums, to see whether they might have violated the Official Secrets Ordinance, Personal Data (Privacy) Ordinance, and immigration services' standing orders. But Democratic Party lawmaker James To Kun-sun said the hunt for the informer was inappropriate. 'This is an issue of public interest, not privacy,' Mr To said. Civil Party legislator Audrey Eu Yuet-mee said the department's actions would deter officers from complaining about illegal and unjust issues in future. Mr So acknowledged on April 8 he had given his name card to his domestic helper of 20 years to submit as proof of his income when she applied to renew her contract in late March. His admission came after media reports based on a tip-off. Yesterday's admission by the department came after further reports on Thursday, quoting anonymous officers. Federation of Civil Service Unions chairman Leung Chau-ting commended the informer's 'courageous action' in disclosing injustice. But the chairman of the Immigration Service Officers' Association, William Lee Hok-lim, backed the investigation. 'This is not a white terror, it is just standard preliminary inquiries to find out the facts,' he said. Ivan Choy Chi-keung, a political scientist at Chinese University, said public interest should override 'internal administrative orders'.