ABOUT 2,000 public housing tenants marched from Chater Garden to the Central Government Offices yesterday to protest against the double-rent policy. The demonstrators represented residents of 91 estates. They were joined by legislators Mr Tam Yiu-chung and Mr Tang Siu-tong. Under the Housing Authority scheme, tenants who have lived in public flats for more than 10 years are required to pay twice the normal rent if their monthly income is more than double the limit for public housing. For example, a family of four with a total monthly income of more than $19,400 will have to pay a ''doubled'' monthly rent of up to $1,600. Legislators passed a motion last December in favour of scrapping the policy, but the Housing Authority claimed the motion was not legally binding. Plans to petition the Governor, Mr Chris Patten, had to be changed because of the annual opening of Government House to the public. The petition was given to a Government House representative outside the Central Government Offices.