"The government has yet to speak to some 30,000 claimants about the changes and only 18,000 have said they will take up the loan option."
SMI had previously been paid as a free benefit covering the interest on mortgages for those claiming benefits such as pensions credit, income support and Universal Credit.
However any payments made after April 2018 will now need to be repaid when the property is sold or transferred into new ownership.
The DWP data shows that out of the 72,000 successfully contacted by phone, 58% have declined the loan and a further 16% are undecided.
A further 27,000 have been sent a letter detailing the changes and contact via telephone has been attempted, while 4,000 have received letters but are yet to be contacted by phone.
DWP stressed that after a loan offer has been given over the phone, claimants have six weeks to make a decision, so those uncontacted will continue to receive SMI benefits until the regulation period runs out.
A DWP spokesperson said: "Over time, someone’s house is likely to increase in value, so it’s reasonable that anyone who has received financial help towards their mortgage should be asked to pay that back.
“People who sign up to the loan will continue to get help with their mortgage interest and it is only repayable if there is available equity when the property is sold.
“If people decide to decline the loan now but change their mind in future the loan can be backdated so in effect there would be no break in payments.
“We have already contacted everyone currently in receipt of SMI to explain the change but we are making sure people have time to review the documents, obtain advice and consider their options.”
However Royal London has repeatedly called on government to delay the changes, warning that those who have not taken up the loan arrangement will no longer receive help with mortgage payments and risk going into mortgage arrears.
Helen Morrissey, personal finance specialist at Royal London, said: “We have repeatedly called on government to reconsider its approach and these figures demonstrate the point. The changes to SMI came in from 6 April and yet these figures show the government has yet to speak to some 30,000 claimants about the changes and only 18,000 have said they will take up the loan option.
"As it stands well over 80,000 people have now lost their mortgage support and we have no idea what strategies they have in place to meet these payments. The likelihood is that we will see people start to default on their mortgage payments.
"The government must put a brake on these changes to ensure these people are engaged with and helped to make an informed decision. Otherwise these people face disastrous consequences.”
