FILM director Ken Loach challenged fellow artists yesterday to support striking National Gallery workers as they marched on Downing Street to demand a halt to hated privatisation plans.

The cinematic veteran, known for films including Kes and The Wind that Shakes the Barley, visited picket lines yesterday morning and said: “It’s a straight choice — which side are you on?”

Workers organised by civil service union PCS are fighting plans to outsource all security and visitor services roles at the Trafalgar Square gallery.

Staff on their fourth stint of strike action since the new year marched down Whitehall yesterday lunchtime to hand over a petition to Prime Minister David Cameron.

Solidarity demos were held in Liverpool, Manchester, Cardiff and Leeds.

“A closed gallery is a very sad sight. (Conciliation service) Acas must be the best place to sort this out,” said video and installation artist Jeremy Deller.

Painter Geraldine Swayne said privatisation would “brutalise” the gallery.

But a number of artists, including sculptor Antony Gormley and photomontage artist Peter Kennard, declined to comment on the dispute when contacted by the Star.

Mr Loach told the Star that big names in the art world were mainly Thatcher’s children.

“They like to revolt but they choose forms of revolt and not political forms,” he said.

“They’ll save the badgers but they won’t get involved in the forces at the core.

“There’s a tendency to think they can shock, but not engage with the core struggle.”

Blasting managers for bringing in security staff with no knowledge of the artwork they supervise, he added: “They’re destabilising and discrediting the workforce in the culture sector, they’re stripping it of knowledge and care. They’re choosing alienation.”

At an open-air meeting, workers discussed strategy and said that the PCS leadership recognised the need to “up the ante” in the coming weeks.

They said that four meetings in Yorkshire on Tuesday had raised an extra £1,300 for the strike fund.

The current strike will conclude tomorrow, when reps are due to discuss potential escalation strategies to deploy if bosses continue to stall negotiations.