Staff at London’s National Gallery have gone on an indefinite strike in opposition to plans for privatisation of the publicly-funded entity.

With privatisation affecting around 400 of the gallery’s 600 staff, approximately 200 members of the Public Commercial Services (PCS) union started the ongoing action on Tuesday (11 August), also protesting the sacking of union representative Candy Udwin.

The privatisation plans mean the gallery will be able to introduce a new roster to "operate more flexibly and deliver an enhanced service". The gallery has said that Securitas has been appointed as its partner to manage some visitor and security services, but that there would be no job cuts and terms and conditions of existing contracts would be protected, despite the fact that about 300 gallery assistants will no longer be employed by the gallery and will instead work for Securitas.

In a statement, the National Gallery said as much of the gallery would be kept open for business during the strike, but added that thousands of school children have had trips to the visitor attraction cancelled because of the industrial action, which has led to 56 days of strikes at the gallery since February, including a 10-day walkout in May.

"We had asked the new director to step in to resolve this dispute before taking over, but now his first week will be greeted by a continuous strike. We remain ready to negotiate,” said PCS general secretary Mark Serwotka.

"We do not believe this privatisation is in any way necessary and we fear for the reputation the gallery rightly enjoys around the world as one of our country's greatest cultural assets."

The strike will be an unwelcome headache for the gallery's new director Gabriele Finaldi, who is due to take over from the outgoing Nicholas Penny next week.