ARTISTS will address coach-loads of demonstrators protesting outside the National Gallery today in one of Britain’s largest ever rallies over a dispute at a single workplace.

Public-sector union PCS has called on members nationwide to descend on Trafalgar Square to demand an end to the gallery’s job outsourcing plans and the reinstatement of sacked union rep Candy Udwin.

Bosses want to outsource 400 of the gallery’s 600 staff.

Today’s rally will be addressed by speakers including Turner Prize-winner Mark Wallinger, film director Ken Loach, comedian Kate Smurthwaite and PCS general secretary Mark Serwotka.

“The National Gallery is a much-loved institution and it must be stopped from damaging its own reputation. It must halt this pointless privatisation and reinstate staff member and PCS rep Candy Udwin immediately,” said Mr Serwotka. “This could be the future for all of us unless we act now. As a new Tory government announces its intention to pass a union-busting bill it is vital that this rally is also a mass protest against victimisation and attacks on our rights.”

Managers have banned union reps from speaking to the press and have been accused of photographing pickets in an unprecedented surveillance operation — an allegation the gallery denies. It issued an invitation to tender for the jobs earlier this month and workers are currently midway through a 10-day stint of strike action, which is the longest so far.

Union reps are hoping that the replacement of retiring gallery chiefs will allow for new movement in negotiations. Gabriele Finaldi will take over as director from Nicholas Penny in August and Hannah Rothschild will succeed Mark Getty as chair of trustees.

A union source said: “The next stage for the strike is to get Gabriele Finaldi and Hannah Rothschild to save the gallery before this lot destroy it.

“We think Finaldi’s appointment was definitely postponed so the decision would be taken out of his hands.

“They thought it was all over when the put out the invitation to tender, but they’re wrong. This is just the beginning.”