The group was transferred to Cardiff from Harmondsworth centre

After visiting the nine men being held at the jail, she urged the Home Office to resolve the situation quickly.

Ms Hart said she was "very concerned" at the use of the prison.

The Home Office has said the situation was a "temporary" measure.

They come from a variety of backgrounds and it's a disorientating experience for them Reverend Aled Edwards

The asylum seekers are being held in Cardiff after being transferred from the Harmondsworth Immigration and Removal Centre, near Heathrow, following disturbances there last month after a detainee committed suicide.

Another asylum seeker from Harmondsworth is being held at Parc Prison, Bridgend.

After visiting Cardiff Prison to see the conditions the detainees are being held in, Ms Hart said on Tuesday: "I understand that the Home Office was faced with practical difficulties in finding accommodation for asylum seekers who had to be moved from the Harmondsworth Detention Centre, following disturbances there.

"However, I am very concerned that prison accommodation is being used in this way.

'Swift resolution'

"The position of the assembly government is clear - that no-one should be treated in a worse way simply because they are an asylum seeker."

She said she had written to the UK Government outlining her concerns and urging the "swiftest possible resolution" to the issue.

She added that she was satisfied that a wider range of advice for the detainees was being made available and said she intended to visit the man being held at Parc.

Leanne Wood, Plaid Cymru's spokesperson on social justice, has also backed calls to release the asylum seekers.

"We all agree that the Home Office on this occasion is wrong," she said.

"People shouldn't be housed in prison if they haven't committed criminal offences.

The party will be staging a protest outside the prison on Wednesday.

"People are very very angry about this situation," she added.

"The assembly has no powers at all over Home Office matters so our hands are tied, but what we can do is put pressure on the Home Office."

The 481 Harmondsworth detainees have been dispersed to prisons and other detention centres across the country - with some being held in police custody, the Home Office said.

All of the detainees were removed from Harmondsworth

A spokesman for the Home Office said that he could not comment on individual cases but said that work was being done to reopen Harmondsworth as soon as possible.

He said that none of the detainees were being held with convicted prisoners and that it was a "temporary situation due to the closure of Harmondsworth".

He added that the detainees would have the opportunity to contact their families by telephone or the postal system.

Reverend Aled Edwards, the church's liaison officer with the Welsh assembly, visited the group on Tuesday.

He said they were very confused.

"They come from a variety of backgrounds and it's a disorientating experience for them," he said.

"They're very upset and some have been distanced from their families in London.