Nepal's labor minister urged Qatar on Monday to scrap a sponsorship scheme which prevents the free movement of migrant workers, calling it a violation of the rights of thousands of its nationals who are working in the Gulf state...The system, which requires migrant workers to seek permission from employers to change jobs, has long been criticized by human rights groups and trade unions who have likened it to a form of modern day slavery....An emailed request for comment on the kafala system sent...to the Qatar embassy....remained unanswered, and Qatari officials were not immediately available for comment by phone.