Portuguese labor groups are vowing to keep up their fight against the government's privatization plans for public transport, as Lisbon subway staff walked off the job for the 43rd time in four years.

Workers at the Lisbon bus company Carris and national railroad company Comboios de Portugal, both state-owned, have also staged dozens of strikes since debt-heavy Portugal needed a 78 billion euro ($85 billion) bailout in 2011.

The public transport companies are deep in the red, and the government is trying to reduce public debt which is around 130 percent of GDP — the third highest in the European Union.

But many workers fear they will lose entitlements and benefits under private management.

The Federation of Transport and Communications Unions said Tuesday's 24-hour strike likely wouldn't be the last.