More than 150 people caught up in a backlog of visa applications have reportedly not been told how long delays might be.
BBC News says British couples kept in separate countries by the backlog have contacted the broadcaster to raise the issue of delays, with complaints of some applications taking twice the usual processing time of three months.
The BBC says British citizen Deon Barnard and his wife Heather, who both grew up in South Africa, applied for a visa on December 23, with Mr Barnard moving to London to start a new job.
He told the broadcaster: “We were expecting, according to our calculations and according to our [immigration] agents as well, about March 28 would’ve been our date of receiving our [visa].
“Heather would’ve been on a plane the next day.
“On about March 26, we got a letter from the [Home Office] that, due to the humanitarian crisis in Ukraine, visa applications were now paused.
“And there was no information, no date, no expectations set, nothing – that was just the end of the story.
“And we’ve been waiting ever since.”
A Home Office official told the BBC: “We are prioritising Ukraine Family Scheme and Homes for Ukraine applications in response to the humanitarian crisis caused by [Russian President Vladimir] Putin’s barbaric invasion of Ukraine, so applications for study, work and family visas have taken longer to process.
“We are working at pace to ensure these are issued as quickly as possible.”
It comes as the Government looks set to face legal action over “unreasonable” delays in the Homes for Ukraine scheme.
Would-be hosts have sent a legal letter to the Home Office over “unexpected, unexplained and unreasonable” delays in processing hundreds of visa applications made in March.
They suggest either the Home Office may be prioritising more recent, simpler applications to “boost” the numbers, and then “boast” about these, or that the policy is “just so incoherent and disorganised” that there is no pretence of processing claims chronologically.
Other areas of concern include MPs being told visas in certain cases have been granted when this is not the case, and sponsors being told cases will be expedited when they have not been.
They also say there are cases where visas and permission-to-travel letters have been granted, but refugees have not been informed or the documents have not been sent or made available to collect.
On Friday the groups Vigil 4 Visas and Taking Action Over The Homes For Ukraine Visa Delays sent a pre-action letter, shared with the PA news agency, informing the Home Office and Government Legal Department they may apply for a judicial review of the policies.
When the legal action was initially announced earlier last week, the Government said it had streamlined the visa system, simplified forms and boosted staff numbers, and it is now “processing visas as quickly as they come in”.
The groups have requested a response by 4pm on Tuesday.