Senior doctors at public hospitals are threatening a mass sit-in in their fight for an extra 3 per cent pay rise from the Hospital Authority - backdated for one year. The Public Doctors' Association is calling on members to put on their uniforms and assemble at the main lobby of the Queen Elizabeth Hospital on Wednesday afternoon for the 90-minute protest. It will be the largest demonstration by doctors since 2007, when 1,300 medics swamped the Kowloon hospital to demand a pay increase. Undersecretary for food and health, Professor Sophia Chan Siu-chee, yesterday expressed concern over the situation, while the authority called for calm and promised more negotiations with doctors. The latest dispute centres on a government decision earlier this year to offer senior civil servants an extra 3 per cent pay rise, backdated to last October, to bring their pay levels closer to those in the private market. The move was based on the civil service pay survey conducted every six years. The association said the some 760 consultants and 1,700 senior medical staff at public hospitals should enjoy the same pay rise, but the authority rejected their demands. Association chairman Dr Pierre Chan Pui-yin said yesterday: "It has been a practice of the authority in the past 20 years or more to follow the government move [on civil servants] to adjust our pay, whether it be a rise, cut or freeze. "But this time the authority has unilaterally scrapped the practice. It will set a very bad precedent and we must not let it happen." Dr Chan said he would not be surprised to see more than 1,000 doctors take part in the protest, as many would be off duty for the Chung Yeung festival holiday. An authority spokesman said it was aware of the doctors' concerns but stressed it could not afford the extra pay rise, which would reportedly cost it more than HK$200 million a year. "The government has reiterated its policy that the civil service pay survey does not apply to aided agencies," he added. However, the spokesman agreed that a competitive pay package would be required to keep staff. "The authority will continue close communication with the staff and hopes the staff's action will not affect services to patients," the spokesman added. But Dr Chan said he was not convinced the authority could not afford the extra pay rise, given its huge surplus. In 2013-14, the government granted HK$45.5 billion to the authority, which recorded a surplus of HK$665 million at the end of the financial year. The authority has said the surplus was due to underspending from a manpower shortfall. Professor Sophia Chan yesterday urged the authority to follow up the issue carefully as "staff morale is important". According to the Civil Service Bureau, there is no policy of linking the staff pay of the subvented sector, including the Hospital Authority, with that of the civil service. The only exception is the salary of teaching staff in aided schools, which is pegged to the civil service pay scales.