Workers at HM Revenue and Customs have voted to take industrial action in a row over jobs and privatisation, adding to the growing number of disputes the government is now facing.
The Public and Commercial Services union said it was fighting against plans to cut thousands of jobs, adding that 30,000 posts had already been lost since 2005.
A trial using private companies to handle tax credit inquiries in two centres in Cumbria and West Lothian is also being opposed.
The PCS said four out of five of its members had backed industrial action short of a strike, and just over half supported walkouts.
The union represents 55,000 members in HMRC, including tax advisers and call centre staff, with a third taking part in the ballot.
PCS general secretary Mark Serwotka said: "When reducing the budget deficit is supposedly the government's number one priority, it makes absolutely no economic sense to cut ever more staff from the very department responsible for collecting the taxes that fund all our other public services.
"The government should be investing to improve services, tackle the tax dodgers and get our economy back on its feet.
"At the same time as cutting jobs and closing offices, we have real concerns about creeping privatisation in HMRC, with public money being handed to companies to make a profit."
An HMRC spokesman said it was seeking dialogue with the PCS and released the following statement: "HMRC is disappointed with the decision to strike and will do everything it can to maintain services to the public.
"We will work to minimise any disruption to customers in the event of strike action."
Driving test examiners, coastguards and other transport staff are to take strike action from the end of the week in protest at government spending cuts, jobs and pensions.
A two-hour walkout will be held next Friday (June 8) by driving examiners, followed by a week-long series of short strikes in the Maritime and Coastguard Agency, all members of the PCS.
Further strikes will be held throughout June by staff at the Department for Transport head office and several agencies including Highways and Driving Standards.
The government is also facing industrial action later this month by doctors, while teachers have warned of co-ordinated strikes in the autumn term if the bitter dispute over pensions is not resolved.