Almost three-quarters of staff at Revenue & Customs say their working experience has deteriorated in the past year - and 53% believe it will be worse still in a year's time.
According to the latest six-monthly staff survey, just 15% of Revenue staff said integration of the Inland Revenue and Customs & Excise had been good for customers, while 50% said it had been bad.
This is in contrast to the position immediately after the merger in April 2005, when 36% thought it was good for customers, against 18% who took the opposite view.
The latest survey was conducted last November, when it was reported the Revenue had lost 25m child benefit records.
The Revenue said it did not wish to shy away from the 'hard messages' in the survey. But it noted that 48% of staff were highly motivated to do their job well - about 10 points up on the previous two years.