New rules that will allow Ukrainian children to come to Britain alone are expected to be announced this week.

It follows revelations in the Guardian that more than 500 children who fled the war without their parents have been stuck waiting in limbo across Europe after applying to the Homes for Ukraine scheme. Most are teenagers who thought they would be eligible and have British families waiting to host them, but who have heard nothing from the Home Office.

The announcement could come as soon as Wednesday, according to a report in the Daily Telegraph, which said under-18s would be allowed to come to Britain unaccompanied if they had written permission from a parent or legal guardian.

A Home Office spokesperson would not confirm any details but did not deny that an announcement was expected on Wednesday. It is understood that the policy will be part of the Homes for Ukraine scheme.

Teenagers travelling without their parents were initially accepted for visas under Homes for Ukraine. A policy banning under-18s from travelling without their parents or a legal guardian was then introduced, but the Home Office did not offer a decision or solution to all those who applied before it was set out.

Beth Gardiner-Smith, chief executive of Safe Passage International, said: “We welcome reports that a new route is to be created for unaccompanied children from Ukraine. It should not, however, have taken this long, with children having been effectively abandoned with the promise of visas that never came through as the government delayed over what to do. Too many children, already traumatised by war, are alone, distressed and vulnerable, with their young lives on hold.”

Nazarii, 17, has been waiting for a Home Office decision from his village in western Ukraine for more than two months while war planes fly overhead. No progress has been made in his case since the Guardian first reported it at the start of May and he has heard nothing from the department.

A teaching assistant and her family in Hampshire have been ready to host him since the application was submitted at the start of April. Nazarii said he was finding the wait and lack of information from the Home Office “impossible” and was relieved that it might soon be resolved. “I’m very happy,” he said. “I hope now that all will be fine with applying.”

The Labour peer Alf Dubs said the government would in effect be returning to its original position, having left teenagers waiting alone in precarious situations. “There’s been absolute incompetence, if not bad faith, all along … It’s unacceptably awful what the government has been doing,” he said.

A government spokesperson said: “It is tragic that children have been caught up in Putin’s war. We have a responsibility to keep children safe and, as the public rightly expect, we have put robust processes in place to protect them once they arrive in the country, working closely with councils throughout.

“Only under-18s who are travelling with or reuniting with a parent or legal guardian in the UK are currently eligible for Homes for Ukraine, but as we have always said we keep eligibility for all our schemes under review.”