London attractions including Tower Bridge and the Barbican could face industrial action following a vote by City of London Corporation staff.
GMB union members working for the council have overwhelmingly voted for strike action, having rejected the Corporation’s 2022-23 pay offer.
Of those who voted, 77% said they were prepared to strike.
Anna Lee, GMB London Regional Organiser, said: “This vote for industrial action shows just how strongly our members feel and how they will continue to fight for a fair and decent pay rise.
“This is an historic vote, the first time ever that City of London Corporation staff have voted to strike over pay.
"I hope in light of this vote the Corporation will reconsider its position and get back to the negotiating table and present an offer which truly recognises the hard work, reliability and dedication of its workforce.”