Section 4 of chapter 151B of the General Laws shall be amended by adding the following paragraph after paragraph 19(a):

                 20.  It shall be an unlawful discriminatory practice for a local or state government entity to discriminate in land use decisions or in the permitting of development based on race, color, religion, sex, national origin, disability condition, familial status, or, except as otherwise provided by law, the fact that a development or proposed development contains affordable housing units for families or individuals with incomes below 80 per cent of area median income. A local government is participating in an unlawful discriminatory practice if the local government was motivated in full, or in part, in its action or inaction on a land use decision or permitting of development by the fact that a development or proposed development contains affordable housing units for households with incomes below 80 per cent of area median income.  It shall not be a violation of this chapter if land use decisions or permitting of development is based on considerations of limiting unreasonably high concentrations of affordable housing. It shall not be a violation of this chapter if a local government entity whose action or inaction has an unintended discriminatory effect proves that the action or inaction was motivated and justified by a legitimate, bona fide governmental interest.