Campaigners have reacted angrily to reports that the Dungavel asylum centre's capacity is to be increased.
Dungavel may be extended to house more people
The Home Office has confirmed that it is looking at a £3m project to increase capacity by a quarter to 194.
This would involve new pre-fabricated buildings with bars on the windows being built at the centre in south Lanarkshire.
The Scottish National Party accused the Scottish Executive of "dishonesty" and of hiding the plans.
MSPs have clashed over who is responsible for Dungavel as the UK Government is currently in charge of immigration and asylum, but education in Scotland is a devolved matter.
An executive spokesman said again on Sunday that immigration and the operation of Dungavel is reserved to Westminster and the Home Office.
A Home Office spokesman said: "This is one of a number of plans to increase the size of detention of state.
"If it goes ahead the capacity will increase to 194. But the extra space will not be used for families and instead will house single males."
Linda Fabiani, SNP MSP for Central Scotland, accused the executive of colluding with the Home Office.
She said: "Ministers are being very dishonest about this. They should be deeply ashamed
at what they are allowing the Home Office to do.
Linda Fabiani claimed the executive had been dishonest
"They're going to have to take notice of the people in Scotland who know that they are breaching human rights."
The MSP claimed the plans were prove that Dungavel was being used like a prison.
She said: "They (the executive) have chosen to make this place a prison and are actually building prison facilities with bars on the windows.
"They are locking children up in that
Labour MSP Elaine Smith, the member for Coatbridge and Chryston, said the plans should have been revealed months ago.
Labour MP Michael Connarty, a campaigner against the detention of children at the centre, said he was concerned.
He said: "We need to move away from this type of facility.
"I'm concerned we seem to be consolidating Dungavel's role. It is a prison establishment and
unsuitable for children."