Portugal’s transport workers’ union, Sttamp, has confirmed workers employed by Groundforce Portugal will walk out on Saturday 31 August and Sunday 1 September.

Sttamp has warned of "severe constraints" at Lisbon and Porto airports, in particular, adding the full extent of any potential disruption couldn’t yet be confirmed.

Its strike notice covers all national airports, which would also include Faro, Funchal and Ponta Delgada, serving the Algarve, Madeira and the Azores respectively.

Sttamp said responsibility lay with Menzies Aviation, which it accused of failing to present any alternative proposal to avoid the strike action taking place.

Menzies Aviation acquired a majority stake in Groundforce Portugal in June. While Portugal’s Tap will be among the airlines hardest hit, Portugal is served by all major UK carriers.

Jet2.com, easyJet, Tui, British Airways, Ryanair and Wizz Air were yet to publicly acknowledge the action on their websites as of Wednesday afternoon (28 August).

Sttamp’s major points of convention include low levels of pay, systematic use of agency workers and overtime demands exceeding legal limits.