The tax authority has faced some critical reports before
Low morale and poor leadership is affecting performance at HM Revenue and Customs, a report by MPs has said.
A staff survey carried out in February 2009 brought "dire results" for the tax authority, the Treasury Committee said.
It found that only 11% of staff felt that change was well-managed in the department.
The poll also found that only 57% of calls made by the public to the Revenue's contact centres were answered in 2008-9.
During the peak period for calls, during July, the response rate was lowest, at just 33%.
"We are particularly alarmed by the low of staff morale and engagement at HMRC, and its effect on performance," said Michael Fallon, the Treasury committee chairman.
"We are deeply troubled by the apparent absence of any plan to ameliorate the situation, and call on HMRC management to re-double their efforts here."
But a spokeswoman for the tax authority said its senior managers were addressing the causes of low morale.
"The department's new business plan includes a key objective to improve staff commitment," he said.
"A top priority for HMRC is to narrow the tax gap and we are fully resourced to do this.
"We focus resources into those areas of the economy that pose the greatest risk of tax loss," he added.
The report's findings came as part of a review of the Treasury and some of the authorities associated with it.
Some Treasury staff faced "burn-out" at a time when the financial crisis was at its peak, the report found.
"Given the extraordinary measures the Treasury and its associated bodies have had to take over 2008-09 in the wake of the financial crisis and subsequent recession - many of which remain ongoing business - it was very difficult to draw final conclusions regarding the level of its success," Mr Fallon said.
The revenue is frequently criticised by the Public Accounts Committee.
Last month it said the HMRC's dealings with older people and their tax affairs was too complex and lead to many of them overpaying tax.
In December 2009 the same committee of MPs reported that the Revenue's ability to collect debts was being undermined by outdated computer systems.
And in June the MPs found that 30% of tax payments were late, and that HMRC was lagging behind in finding ways to chase them.