Unite has criticised reported plans from Heathrow Airport to fire and rehire staff on inferior contracts.
The union said the move undermines a vulnerable industry at a critical time.
Reports suggest Heathrow Airport Limited has issued a formal ‘section 188’ notice to begin the consultation process.
The airport wanted job losses would be needed earlier this year, as the Covid-19 pandemic saw travel come to a virtual standstill.
In response to the proposed cuts, Unite last month negotiated proposals to cut pay by 24 per cent for some workers.
There are also plans to cut allowances, impose inferior conditions and to close the company pension scheme.
Unite is currently putting the proposals to the workforce in a consultative ballot.
Unite regional co-ordinating officer, Wayne King, said: “Heathrow’s actions are extremely unhelpful and further undermine confidence in the industry.
“Our members have worked tirelessly throughout Covid-19 pandemic to conduct industrial relations via the media in such a brutish manner is designed to create fear and panic in a group of key workers.
“Heathrow’s actions have made already difficult negotiations even more fraught.
“Unite is currently balloting its members on the proposals Heathrow’s actions demonstrate that it is not prepared to allow democracy to run its course.”
King added: “At a time when Unite is working hard to persuade the government to follow the lead of other European nations and provide specific financial support to the aviation sector to ensure that the industry and workers can survive the pandemic and thrive in the future, these actions are distinctly unhelpful.
“It should not be forgotten that Heathrow is an incredibly wealthy company at the start of the pandemic it boasted of a £3.2 billion war chest.
“These attacks in pay are not about survival but introducing measures to boost future profits.
“Unite urges Heathrow to withdraw this ill-judged attack on its loyal workforce and to return to the negotiating table as had been previously agreed.”