Border force strikes continue at Melbourne Airport

Melbourne Airport public servants are on strike today over stalled pay negotiations.

The strikes, organised by the Community and Public Sector Union, began at 4am.

Critical security staff will not be involved in the work stoppages.

"While the likely level of participation is unknown, we strongly encourage airline and cruise ship passengers to plan for potential delays by arriving at international airports and cruise ship terminals even earlier," the Department of Immigration and Border Protection said in a statement yesterday.

The second day of strikes follow calls from Immigration Minister Peter Dutton for border staff to return to work, saying the terror threat is still too high.

The threat hasn't passed within a couple of days following the Brussels attack," Mr Dutton told ABC Radio.

"These rolling strikes aren't welcome and I hope that they come to an end sooner than later."

Union national secretary Nadine Flood said workers were striking as a last resort, as part of a two-year negotiating battle with the federal government over pay and work conditions.