The Department for Work and Pensions has lost more employment tribunals for disability discrimination than any other employer in Britain since 2016.
BBC Panorama found the DWP lost 17 of 134 claims of discrimination against its own disabled workers from 2016-19.
And it paid out at least £950,000 in both tribunal payments and out-of-court settlements in that time.
The DWP said it was "shocked" by the data but was reviewing its processes to ensure all staff were treated fairly.
It is the government department that is responsible for supporting people with disabilities into employment.
Of its 80,000 members of staff, 11,000 identify as disabled.
Panorama analysed the publicly available data on the online Employment Tribunal decisions database up until December 2019.
It reveals that the DWP had more cases in total and more cases which it lost than any other employer.
A comparison with the five employers who had the largest number of disability discrimination cases also showed that the DWP had more cases and more tribunal defeats in proportion to its total number of employees.
Karen Jackson, a leading disability discrimination lawyer, said: "There is a horrible irony that the organisation that is designed to look after the more vulnerable members of our society is constantly falling foul of the Equality Act around disability.
"To me, that can only suggest that there is something quite fundamentally, systemically wrong within the culture of the organisation."
Barrie Caulcutt, 57, was awarded £26,000 after he took the DWP to an employment tribunal and a judge ruled he had been discriminated against because of his disability.
He worked in the finance department at the DWP for 30 years and suffers from a serious panic and anxiety disorder that can trigger life-threatening asthma attacks.
But he was not able to manage his condition after being moved into a different job role.
"I basically told them I couldn't do the job I was doing, because of my disabilities. I provided evidence from my GP," Mr Caulcutt said.
"Their own occupational health service told them that unless they moved me from the environment I was working in, it would be of detriment to my health."
As part of his new role, Mr Caulcutt was told to attend a training session in a small room. He said said he could not attend because he suffered from panic attacks but was told he would be disciplined if he failed to show up.
Mr Caulcutt said that during the course he had an "overwhelming feeling" that he had to leave the room.
"I just collapsed to the floor. I realised then that it was an asthma attack. I'm not a religious person, but I was praying. I was praying. Please, God, don't make me die. Don't make me die now," he said.
"And the next thing I was in the back of an ambulance and they were rushing me to hospital."
Despite knowing Mr Caulcutt had been admitted to hospital, the next day his managers called him to ask where he was.
During the tribunal, the judge described his treatment as "wholly inexcusable".
'Dismissive' and 'nasty'
The DWP has lost 12.5% percent of its employment tribunal cases for disability between 2016 and 2019.
On average over this period 3% of disability discrimination claims were lost by employers.
One the biggest payouts made by the DWP for disability discrimination was awarded to former benefits worker, Charlotte.
Charlotte suffers from serious health problems, including depression, and was sacked by the DWP for taking too much sick leave.
She said her colleagues were often "dismissive" and "quite nasty" when discussing state benefits claimants and she felt they had the same attitude towards her.
"I think that me being disabled, I kind of felt like if I had time off, people thought I was lying or faking it or I wasn't really ill, and that was kind of a culture," she said.
At Charlotte's employment tribunal, the judge found she had been unfairly dismissed and discriminated against by the DWP.
From 2016 to 2019 the DWP paid out at least £953,315 to DWP employees with disabilities as a result of losing employment tribunals, or because they settled out of court.
Freedom of Information requests reveal that between April 2017 and June 2019 the department settled 45 claims out of court, at a cost of £713,000. The remaining £240,000 was awarded to people who had won their employment tribunals.
'More we can do'
A spokesperson for the Department for Work and Pensions said: "We are shocked that, when presented in this way, the data shows us in this light."
The department said it ensured staff had formal and informal routes to raise any concerns and that cases brought against it came from fewer than 2% of staff with disabilities - although it acknowledged the figure was "still too high".
"Fair and respectful treatment is a right and we do not tolerate discrimination in any form," the spokesperson said.
The DWP said it had improved how it managed absence and resolved complaints, as well as introducting 1,600 mental health first aiders, adding: "We know there is always more we can do.
"We have instigated a review of our processes and actions following tribunal cases, to ensure all our employees are treated fairly and with respect."
You can watch The Million Pound Disability Payout on BBC One at 20:30 GMT on Monday.