When employees at the opaque Dublin Cessation Team – until last week called the Third Country Unit – tell fellow Home Office colleagues where they work, there is a hush.

“The DCT – and the TCU before that – is notorious within the Home Office, so their faces drop and they ask if all the rumours are true. When we say they are, they just say they’re ‘so sorry’,” said one of the multiple DCT employees who have spoken out about conditions at the unit.

The DCT is a central cog in the Home Office’s machine managing asylum in the UK. Based at Lunar House in Croydon, south London, the 50-odd employees work in one open-plan room in cramped, airless conditions: they sit at desks so tightly packed they can read each other’s computer screens and have no room for their papers. Through windows that won’t open, they look out on an endless vista of concrete.

“The DCT – and the TCU as a whole before it was moved to Glasgow in early April – is a unit where good, hardworking colleagues with a positive outlook are persistently undermined, belittled and sadly, in many cases, bullied. They are subjected to dubious disciplinary processes, and even dismissal,” one whistleblower alleged.

The sources, all of whom are either still working at the DCT or were until very recently, describe a unit where bullying is rife.

I love my job and what I do, but I am miserable and desperate

“The DCT is a timebomb waiting to blow,” one said. “There’s a toxic atmosphere across the whole department. Our colleagues are beyond miserable.”

Another spoke of a culture of fear and “immense bullying” where favouritism is rife and “you’re treated like an enemy by the management if you’re not in their clique”.

“One of the managers makes sexual boasts about the number of women he’s slept with, makes violent boasts about wanting to punch people in the face, and boasts about wanting to fire people – which he has done on at least one occasion without offering that person extra support before he forced them out,” the whistleblowers claimed.

One staff member allegedly put in a grievance against managers that should have been dealt with in five days. The grievance was submitted in August last year but has still not been addressed.

The ill-treatment of staff has a direct impact onthe UK’s most vulnerable people, the whistleblowers said, with administration errors leading to people being unlawfully detained.

“There is a very high human cost to all this,” one source said. “The culture is leading to people who have sought asylum here being detained – always without warning – for up to six weeks, but then those detentions are frequently proved later to be unlawful.

“This not only means these poor people have been ripped away from their families and homes but that the government then has to make huge payments to them – using taxpayers’ money – in recompense.

“There was one person in the detention centre recently for four weeks who, it eventually turned out, hadn’t even accepted that the immigrant was their responsibility.”

One of the key criticisms is that when a decision is made to refuse an application, the asylum seeker is automatically detainedwithout warning for up to six weeks until they are removed from the UK.

“Some EU states will not detain applicants because it’s not been proven to be necessary or proportionate. But despite a highly critical 2015 court case concerning unwarranted detentions, the DCT doesn’t even attempt non-detained removals,” they alleged.

Detentions cost the British taxpayer £108m in the year ending 31 March 2018, while the Shaw report found it costs £85.92 a day to hold someone in detention.

Until last week, there were four teams in the TCU: the decision team, the barrier team, the removals team and the asylum team. In early April, the work of three of those four teams moved to Glasgow . All TCU employees remained in London, however, and were moved into the asylum team to deal with the backlog of cases.

“The backlog we’re dealing with is humongous,” a source said, pointing out that the number of caseworkers able to make decisions on the barrier team fell from six in December 2018 to two before it was shifted to Glasgow.

“I’m working on cases from early 2016 that should have been dealt with in six months,” the whistleblower added. “Before the move, the cupboards were stacked with documents that we simply didn’t have time to deal with. Often we found medical reports from Freedom from Torture, which had been overlooked in the chaos and hadn’t been linked to the applicants’ file. This means their application potentially went through without all the information needed to make a fair decision.”

The TCU was criticised in a report in 2015 by David Bolt, the chief inspector of borders and immigration.

When it was all in London, the TCU was a tight-knit team but the wider environment was so bad that, sources say, on average an employee left every two weeks. Its name might have changed, but conditions remain the same, the sources claim.

On one recent day there were three farewells in one hour. “The turnover is exorbitantly high,” said one source. “Everyone is leaving for the same reasons: bullying, oppression and mistreatment.”

The whistleblowers also alleged that TCU employees without sufficient security clearance were, until recently, told to use an IT system connected to MI5 and other secure government networks, including the police national computer and terrorist watchlists.

The Warnings Index Control Unit (WICU) network tracks people who have been charged with immigration offences. It should only be used by staff with high-level security check clearance but since it was installed at the TCU around three years ago, staff with lower-level counter-terrorism check clearance have been inappropriately told to conduct checks on the system, the sources said.

The alleged practice was apparently only stopped in January when an internal Home Office WICU trainer realised staff did not have the required clearance. . But the whistleblowers say they believe the alleged security breach was not reported to the other secure networks that might have been compromised by it.

Other allegations include the fact that confidential emails were regularly sent from TCU secure systems to insecure external email addresses despite employees having warned management these emails could be hacked. The emails contain details including asylum seekers’ addresses, date of birth, medical history, reasons for seeking for asylum, and the route they have travelled across Europe to reach the UK.

“It’s a gross security breach,” claimed a source.

The whistleblowers paint a picture of a department in chaos: “Correspondence trays have become mountains, with backlogs of up to two years, and Home Office files, valuable documents and submitted evidence scattered all over the place.”

One source said: “I love my job and what I do, but I am miserable and desperate. I sit and watch as colleagues who I would consider friends are bullied and left in tears, constantly paranoid and made to feel like they’re worthless and stupid. I’m talking about educated graduates who end up mentally exhausted and destroyed but too scared to even take sick leave because they end up being disciplined and thrown out.

“I can’t physically cope with the workload and I can’t even tell anybody about how I feel because I’ve seen what has happened to people before: they get labelled as troublemakers and all of a sudden leave the unit – resign or move to a different unit. Some days, I come home after another day of hostile environment and I break down, suffer from panic attacks and feel terrified of going back the next day.”