MPs will discuss the impact of a so-called "bedroom tax" which will impose an under-occupancy penalty on tenants.
Newport East MP Jessica Morden hosts a debate later over changes which will see housing association and council tenants have housing benefits cut if they are deemed to have spare bedrooms.
Mark Littlewood, director of think tank the Institute of Economic Affairs, admitted it was a "far from perfect" solution, but said it was a "pretty good second best solution".
He told BBC Radio Wales: "Housing benefit is costing the country a small fortune.
"I think if you are on housing benefit ... then it is only reasonable that you respect the scarcity of housing that is around.
"It is not really acceptable, without some sort of penalty, that, say, two people live on housing benefit in a house or a flat that's more than capable of housing five or six people."