Over 11,500 angry tweets were sent to HM Revenue and Customs (HMRC) for making callers wait an average of 47 minutes last year.
According to research by Citizens Advice, one caller had to wait an hour four times to get through to HMRC.
The research studied 34,000 tweets made between August 2014 and August 2015.
Last year, HMRC came under fire after government showed that 17 million calls to HMRC went unanswered.
Gillian Guy, chief executive of Citizens Advice, said: “Work and caring responsibilities means not everyone will be able to wait for three quarters of an hour to ask HMRC a question.
“We have consistently raised this issue with the Government. But evidence from across the Citizens Advice service, and our new research, shows HMRC is still failing to provide a timely service.
“There is already a clear demand to be able to speak to HMRC. With the roll-out of Universal Credit and big changes to tax credits just around the corner this is only going to grow.”
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