The PCS union held a rally outside parliament on Tuesday against Tory plans to close tax offices and slash thousands of jobs.
HM Revenue and Customs (HMRC) bosses issued 150 compulsory redundancy notices last month.
They also announced plans to close 137 tax offices and axe up to 8,000 jobs last year.
The PCS has said it is considering industrial action.
Its HMRC group executive was set to meet this week.
PCS general secretary Mark Serwotka told the rally, “We need to challenge them industrially. There will need to be industrial action unless there is a pretty urgent change of heart from George Osborne and the Tories.
“We’re not just talking about protest—we’re talking about something that will make them sit up and take notice.”
It will takes strikes to save jobs. Action at HMRC could lead the way for a fightback in the civil service and public sector.