Housing Minister Tim Mander said public housing tenants are required to pay up to 25 per cent of their assessable household income in rent, but exemptions for some welfare payments lowered the contribution amount for some tenants to less than 10 per cent in some cases.

Family tax benefit part A and B, child support payments and the large family supplement will no longer be assessed at a lower rate or overlooked as assessable income altogether in a bid to recoup an estimated $100 million in lost rent.

Mr Mander said under the new rules all tenants' rent would be calculated in the same way.

``On one hand we had people receiving hundreds of dollars each week off the books, and on the other we had people on the aged pension or singles working low income jobs who weren't getting the same privilege,'' he said.

Centacare assistant director and regional manager (West) Marilyn Jacob said one blanket rule for all tenants appeared equitable and `fair' but warned it might not be flexible enough to account for people's individual circumstances.

``For some, this shift in how their income is assessed may spill them over the Department of Housing and Public Works income threshold for eligibility for public housing.''

According to the Department of Housing and Public works public housing tenants pay on average $126 a week.