The spokesman was responding to claims by Simon Burgess, director of insurance provider British Money, who had said that incoming changes to the benefit were the equivalent to “daylight robbery” for householders.
SMI provides unemployed homeowners with certain income-related benefits that help towards interest payments on their mortgages.
From April 2015 it will become a repayable loan, charged to the property as part of wider benefit reforms.
Mr Burgess claimed the reformed benefit could charge homeowners up to 8 per cent in interest in addition to the repayable loan amount.
He added: “Mortgages are now available at 3 per cent, so how can the DWP justify a rate which is nearly three times higher?”
However, a spokesman for the DWP said any plans to impose additional charges on beneficiaries would “need new legislation”, while no decision had been taken to date.
Ian Gwinnell, director of Staffordshire-based IFA All Counties Financial, said SMI had helped a number of his clients during the past, but added that public sector cuts made the government’s reform of the benefit inevitable.