SERCO, which is threatening to make up to 300 asylum seekers homeless in coming weeks, has been accused of “callously” changing the goalposts on the eviction process without warning, as it emerged that letters issued last week gave just 14 days notice of lock changes rather than the 21 days agreed by the Home Office.

Scottish Refugee Council said 20 “panicked” people with the new 14-day lock change notices had presented themselves to its service last week. Other charities, including the Asylum Seeker Housing (ASH) project, have also seen distressed asylum seekers with the “threatening” letters.

The new process has been rolled out without warning, despite initial commitments made by Serco that it would provide 14 days notice of eviction before – following “further criteria checks” – a lock change notice with seven days notice was delivered.

In June UK Immigration Minister Caroline Noakes wrote to all seven Glasgow MPs to lay out the process and “provide some reassurance”. However yesterday a Home Office spokeswoman said it “had no authority” to sanction Serco’s decision to change the agreement.

Charities said the decision underlined the need for legal oversight of the eviction process, granted to everyone else under Scottish Housing law. Govan Law Centre’s appeal on Lord Tyre’s decision that lock changes could be carried out without court orders is due to heard in late August, just days before Mears Group is due to take over the Home Office contract t provide asylum seeker housing.

Graham O’Neill, Scottish Refugee Council’s policy manager, said: “This is a new arbitrary process sprung on vulnerable individuals and those trying to help them. It is being rolled out without warning. It’s further evidence of how in this sphere of eviction and street homelessness, the Home office and its contractors can just shift the goalposts.

“The agreed procedure was set down clearly by the minister in June to MPs, so this change illustrates clearly the legal and procedural vacuum here. But if you can’t trust a minister writing in that capacity, then what can you trust?

“We urgently need both legal and procedural safeguards, as the consequence is street homelessness. This is why it is so important that the Court of Session is considering this lawfulness of evictions with no court oversight, and worse still that this happens via the traumatic and callous method of forced lock changes.”

Sheila Arthur, manager of the ASH project, said Serco had “callously upped the ante” with letters threatening that as well as changing locks, people’s belongings may be confiscated if they are in the property. “Many of our service users received these letters over the last few days and have called us understandably very upset and worried that they will be out on the streets in a matter of days,” she added.

“It must be borne in mind that many asylum seekers have significant mental health problems and letters like these potentially have a massive impact on their health and wellbeing. We once again urge the Scottish Government to intervene and put an end to the callous practices of this private company before their actions result in tragic consequences.”

Paul Sweeney, Labour MP for Glasgow North East, where many facing eviction are living, said: “This is typical of Serco. “

Its attitude as the contract is due to change hands is just to clear this problem off its balance sheet. It’s really just a cleaning-up job for them. It wants this liability off its books, and the Home Office is complicit in this.’’

He claimed that it meant that vulnerable refused asylum seekers – the majority of whom were still in discussions with lawyers about possible legal remedies for their case – were being left “on a cliff edge” .

Julia Rogers Serco managing director for immigration, said: “The legal minimum notice we have to give former asylum seekers who are still living in the properties that we are providing them free of charge at our own expense is seven days, although over the past few weeks we have chosen to give significantly more notice than this minimum requirement.

“Given that we will reach the end of the contract at the end of September, we now have to reduce the minimum notice, we will give former asylum seekers to 14 days.”

A Home Office spokesperson said that it did not have “the authority to sanction Serco’s actions as those affected had “no legal basis” for asylum support. “We take the wellbeing of asylum seekers and the local communities in which they live extremely seriously,” she added. “Together with charities, we have engaged with every individual affected over a number of months to provide advice and guidance on the support and options available to them.”