As Hollywood braces itself for another disruptive strike – this time by actors – the union that represents some of the industry’s biggest stars has been accused of a “ferocious attack” on a rival guild to strengthen its hand at the bargaining table.

The Screen Actors Guild has been unable to reach agreement on a new work contract for its 120,000 members after its existing deal expired on Monday. It has since held talks with the studios about a final offer even though it has hinted it would be rejected regardless.