Workers employed at Gatwick Airport to help passengers with reduced mobility are to vote on strike action in a row over pay.
Members of Unite employed by The OCS Group have rejected three separate offers during a long-running dispute.
The union has 200 members with the company and said the majority are paid just £7.65 an hour.
The OCS Group said it was in "active discussion" with the union and hoped for a "swift resolution".
Unite regional officer Jamie Major said: "OCS doesn't seem serious about settling this dispute.
"At the last meeting, management gave four separate options, none of which represented an improved offer...
"OCS was simply manipulating figures to rob better paid staff to fund workers on poverty pay."
In a statement, the company said: "OCS is sorry that we have ended up in dispute... We hope for a swift resolution and we will be working towards that goal in the coming days.
"OCS has made a serious offer to our staff and we remain in constant contact with them and the union.
"We have responded to an invitation from Unite today to further talks and hope to arrange to meet in the coming week for further discussions."
The ballot opens on Thursday and closes on 9 March. Unite warned of "significant strike action" if there is a yes vote.