There was no consultation with local communities or the Welsh Government over possible plans to house about 250 asylum seekers at a military base, it has been claimed.
The Penally Army centre in Pembrokeshire is one of several sites being considered by the Home Office.
But the Welsh Government said on social media it had not been approached.
The UK’s Welsh Secretary Simon Hart said he was seeking “further clarification” on the proposals.
In a statement on Twitter, Welsh Government officials said: “The UK Government didn’t consult the local community, local services or us about their plans to use a military base in Wales for asylum seekers.
“We believe people fleeing war and conflict deserve the best possible start in a new country.
“We must do better.”
The Home Office said it was working with the council and police to ensure “vulnerable asylum seekers” had suitable accommodation.
Facilities in south-east England are under strain, so people seeking asylum may be sent to Pembrokeshire instead.
“During these unprecedented times, the government is working with a range of partners and across departments to secure further accommodation and the MoD has offered use of some of its sites,” said a Home Office official.
“When using contingency accommodation we work closely with organisations, including local authorities and law enforcement, throughout the process to ensure value for money and that vulnerable asylum seekers, who would otherwise be destitute, have suitable accommodation while their claims are processed.”
Confirmation about the possible plans led to a protest from local residents on Tuesday.
The Police and Crime Commissioner for Dyfed-Powys Dafydd Llywelyn said he had written to Home Secretary Priti Patel over the issue.
“I am deeply concerned about the lack of clarity relating to the proposed arrangements,” he said.
“Greater strategic planning and engagement is needed to ensure we support and safeguard these vulnerable individuals and respond to local concerns.”
Simon Hart, who is also the MP for Penally, said he appreciated residents were “concerned about a number of issues” which he had raised with Priti Patel.
“For example, I have asked how long the site will be used, what the security arrangements will be and whether the Home Office will be funding any additional costs that Pembrokeshire County Council, Hywel Dda Health Board and Dyfed Powys Police might incur.”
He said he would publish replies on his Facebook page as soon as he received them.
“In the meantime I am keen to avoid too much speculation in case this causes increased tension and concern.”