The Hollywood actors’ strike could be moving across the Atlantic if US production companies shift filming to the UK because of the industrial action taken by their American counterparts, a British union has said.

Equity, which represents more than 47,000 performers in the UK, says the union stands in solidarity with US actors who are striking in a dispute with Hollywood studios.

The union – which is not striking – told US companies it will be keeping a “very close eye” on any attempts to move productions to the UK due to the action called on Thursday evening.

Yesterday, Robert Downey Jr, Cillian Murphy, Emily Blunt and Florence Pugh staged a walkout of the London premiere of historical epic Oppenheimer due to the strike.

Equity’s general secretary Paul Fleming told the PA news agency he is “hopeful” a settlement with members of the Screen Actors Guild – American Federation of Television and Radio Artists (Sag-Aftra) will come soon.

He said: “Anything that happens on a British contract, we’re looking to next year’s negotiations.

“The one exception is if there are productions from the United States that attempt to avoid the industrial action by relocating to the United Kingdom – we are keeping a very, very close eye on them.

“We do reserve the right to use British legislation to take British industrial action in those sorts of instances and that will be on a case-by-case basis.

“I can’t say the law here is significantly more restrictive than the United States in terms of how you take a strike, but we will be clamping down on those sorts of productions.

“And also a huge issue for Sag-Aftra members for the last month or so has been an adverts for British productions which say ‘no Sag-Aftra member need apply’.

“Well, I’m sorry, this contract is not in dispute and discrimination on the grounds of a trade union membership is illegal in this country, irrespective of where that trade union is based.

“So that’s where things might get a bit more heated this end.”

It comes amid the ongoing industrial action by more than 11,000 members of the Writers Guild of America (WGA), who began industrial action on May 2.

Among the productions in the UK that could be affected by the strike action is the filming of Deadpool 3, starring Hollywood actors Ryan Reynolds and Hugh Jackman.

House Of The Dragon series two with Matt Smith and Emma D’Arcy could also be affected, alongside the second series of The Sandman with Tom Sturridge and the fourth series of Slow Horses with Academy Award winner Gary Oldman.

Speaking about the impact on the British film industry, Mr Fleming said it depends on whether an actor is under an Equity or Sag-Aftra contract.

He said: “So a Sag-Aftra or an Equity member working on an Equity contract is not on strike because that’s not the contract in dispute.

“Where it gets a little bit more complicated is that there are some Sag-Aftra members around the world who are working on Sag-Aftra contracts alongside others who are on Equity contracts.

“So imagine something that shoots in multiple locations, for instance, and (the actor) might be on a full American contract, their position is more ambiguous and more complicated.”

He said that if the dispute goes on then there will be a “major impact” as British actors working on American contracts are now on strike.

Mr Fleming said: “The vast majority of shows that are recorded principally in the UK or in Europe are on our agreements so that’s the consequence but there will be some that stop.”

He said the studios, production companies and streamers are not “going to win” as actors’ resolve is “absolute”.

Mr Fleming added: “Our view is that we have complete and utter solidarity and support with Sag-Aftra.

“We will do all we legally can do to support and uphold their industrial action, and the message to the producers who operate over here is: get your house in order, get to the table quickly. before this starts impacting the global industry.”