General secretary of the Public and Commercial Services (PCS) Union, Mark Serwotka, reportedly said Number 10 could face "post-strike action litigation" over its airport contingency measures.
Around 1,000 Border Force officials at six major UK airports embarked on their second four-day walkout over the festive season on Wednesday (28 December), but there were few delays due to military personnel and civil servants being deployed to cover the striking workers.