Current amount does not encourage take up of the sponsor scheme
Campaigners are urging support to double monthly payments to families hosting Ukrainian refugees.
It comes as Britain's refugees minister said that vulnerable migrants could end up homeless once the current placement period ends.
Under the UK's Homes for Ukraine scheme, hosts are given £350 a month to house refugees from the eastern European war zone for a minimum of six months.
About 25,000 offers of accommodation have been taken up so far, with an average of three Ukrainians living in each home, says minister Lord Richard Harrington.
Lord Harrington says he is working "very hard" with the UK Treasury to double the monthly “thank-you” payment for sponsors who house refugees for longer than half a year.
"The costs … they’re paying maybe a big chunk of rent themselves, the mortgage payments have gone up and everything, and I think it’s perfectly reasonable, in my view, to increase the amount that we’re paying them," he said.
Positive Action in Housing (PAIH), a refugee homelessness charity which started the country’s oldest hosting network, said there is no system in place for a third party to support or manage the hosting placement.
It added that the UK government never thought it through and never consulted experts in the field or even considered how to manage the hosting relationship and make it sustainable and avoid homelessness.
Robina Qureshi, PAIH’s CEO, added: "Our Room for Refugees Network has been running since 2002, we manage the hosting relationship so that arrangements can be brought to an end easily, or extended if all is going well.
"It is unrealistic to assume that Ukrainian refugees will just move on to new accommodation when there are pre-existing housing shortages and homelessness across the country. Rent deposits are also prohibitively expensive. It remains to be seen whether extending or doubling the £350 payment makes a difference. But if people are already barely tolerating each other in the same living space, it won't make a difference. It will be the refugees who must leave.
“In the absence of a proper system, we would encourage hosts and guests to have a conversation at least a month before the end date about when is a suitable exit date. Guests may need help to find alternative accommodation or assistance with presenting themselves as homeless to local authorities.
“The worst case scenario is where a host feels obliged to keep their guests in their homes without a resolution or end in sight."
More than 115,000 Ukrainians have arrived in the UK under visa schemes, latest government figures indicate, including 81,700 refugees under the sponsorship scheme.
The Sanctuary Foundation, a charity that helps to support Ukrainian refugees and sponsors, is launching a campaign — Not Too Late To Host — with the matching service Opora to encourage more people to offer sponsorship.
Dr Krish Kandiah, the group's director, said the need for hosts was now “even more desperate”.
“War has spread across the country over the past six months and lives have been torn apart," he said.
“Neighbouring countries are struggling to cope. This is why we are urging more British people to welcome Ukrainians into their homes.”