HM Revenue and Customs could be facing a stress crisis as half of its staff say they are moderately or highly anxious.
The shocking figures were revealed in the department's employee engagement survey, which was conducted in autumn last year.
The HMRC People Survey 2013, which questioned more than 30,000 workers and was part of the Civil Service-wide survey of staff attitudes and experiences of work, recorded that 31% of the department's employees said they felt completely anxious and 19% of the respondents said they felt moderately anxious.
The research also revealed only 24% of the workers would recommended HMRC as a "great place to work" and less than two in ten (17%) of respondents felt "positive" about the statement: "when changes are made in HMRC they are usually for the better".
"These new figures suggest that there are high levels of anxiety among staff employed by the HMRC, with half of employees saying that they felt moderately to very anxious on the previous day," Emma Mamo, a policy and campaigns manager at mental health charity Mind, told IBTimes UK.
She added: "Most staff will experience stress – excessive workload, tight deadlines and poor relationships with managers are all common sources – but there are many ways that organisations can minimise these stressors.
"It is vital managers meet regularly with staff, especially when there are changes occurring that will impact staff wellbeing."
But the survey also found that a vast majority (79%) of HMRC workers were happy with the department's organisational objectives and purpose.
In addition, three quarters (75%) of the questionnaire's respondents said they are sufficiently challenged by their work and more than eight in ten (82%) of employees said they are interested in their work.
The department's overall employee engagement score was 43%. To put that in perspective, the polling company Gallup have described "world class" levels of employee engagement as 67%.
"It is no wonder the levels of stress and anxiety are high in HMRC," a spokesman for the Public and Commercial Services union told IBTimes UK.
He added: "This is a department that is responsible for collecting the taxes that fund all our other public services and yet resources have been systemically cut by successive governments, leaving those who remain unable to cope."
The figures follow a recent report by the Public Administration Select Committee, which called for the establishment of a Parliamentary Commission into the Civil Service.
"The aim of the commission should be to ensure that the Civil Service has the values, philosophy and structure capable of constant regeneration in the face of a faster pace of change," the report explained.
"The importance of the review to the future working of government in this country means that it is fitting for the Treasury to fund this work, in the same manner as the Parliamentary Commission on Banking Standards."
HMRC had not responded to a request for comment at the time of publication.