Around 80 workers across aviation rescue and firefighting services, airfield operations, airport control and car parks are expected to join the walkouts between September 13 and September 26.
During a consultation ballot, 68% of GMB union members at John Lennon turned down the airport’s latest offer of a 2.2% pay increase.
The union said the airport’s offer of 2.2% and a £150 lump sum still fell short of its demands, which it says it has reduced from 3.6% to 3% in an attempt to stave off further strikes.
Members have previously staged around 48 hours’ strike action over the issue.
The GMB says the deal still came in below inflation and would mean a “real terms pay cut” for members.
It has now committed to four 12-hour walkouts between 7am and 7pm on September 13, September 19, September 24 and September 26, and has threatened to hold a minimum of a further eight days action during October.
Eddie Parker, GMB Organiser, said: “It’s not surprising GMB members rejected Liverpool Airport Ltd’s new pay offer – because to accept it would mean a real terms pay cut for them.
“The company really don’t seem willing to compromise – increasing their offer by just 0.2%. Meanwhile, we dropped our expectations by 0.6% to try an avoid industrial action.”
Parker added the union was willing to get round the table with the airport to resolve the issue.
In a statement, the airport said its improved offer was backdated to April 1 and in combination with the £150 one-off payment, represented an average pay increase of 2.7% - above the Consumer Price Index inflation rate of 2.5%.
To date, two strike periods have already taken place totalling 48 hours of industrial action, including over the busy Bank Holiday weekend,” said the airport.
“However, robust contingency plans... have ensured passengers have continued to receive excellent customer service throughout as usual. There have been no delays to any flights or disruption to passengers as a consequence of this industrial action.
“These plans will remain in place during any future strikes to ensure it remains business as usual throughout all further industrial action too.”