WORKERS at Britain’s troubled National Gallery have warned bosses of a summer of discontent if they refuse to return to negotiations.

Gallery workers have walked out on strike on almost 50 days this year over plans to outsource security and visitor services staff at the Trafalgar Square institution.

Walkouts are planned for every week this month — but public-sector union PCS is threatening to escalate action further when new director Gabriele Finaldi and new chair of trustees Hannah Rothschild take over.

PCS general secretary Mark Serwotka has written to trustees individually to formally request talks on the union’s proposals for flexible contracts to allow the late opening that the gallery says requires outsourcing.

Outgoing director Nicholas Penny was reported recently to have a preference for staff remaining in-house. 

Last weekend Mr Penny faced sharp criticism for his handling of the dispute from former department of painting senior curator David Jaffe.

Mr Jaffe told the Sunday Times that the outsourcing “doesn’t even save money” and would undermine the visitor experience as contractor security guards would “get told they don’t need to know anything about the paintings.”

PCS rep Candy Udwin, who was sacked after telling a union officer about the cost of outsourcing, will have her case heard at an tribunal in October. 

She was put back on the payroll last month after a preliminary hearing found it was likely she had been victimised for union activities.