The Old Vic theatre claim 20 people have accused Kevin Spacey of sexual misconduct.

The London theatre opened up an investigation into the disgraced 'House of Cards' star following allegations he had sexually assaulted young men during his stint as artistic director there between 2004 to 2015, and they received a number of personal testimonies of alleged inappropriate behaviour from the actor.

The theatre claimed a ''cult of personality'' had existed around Spacey, and his status and stardom had stopped people, in particular young actors and junior staff, from speaking out about his alleged actions.

They said in a statement: ''Despite having the appropriate escalation processes in place, it was claimed that those affected felt unable to raise concerns and that Kevin Spacey operated without sufficient accountability.

''This is clearly unacceptable and the Old Vic truly apologises for not creating an environment or culture where people felt able to speak freely.''

And Old Vic chairman, Nick Clarry, apologised to those who ''felt unable to speak up'' at the time and vowed to promote a ''safe and supportive environment'' at the venue.

He said: ''Inappropriate behaviour by anyone working at the Old Vic is completely unacceptable. We will foster a safe and supportive environment without prejudice, harassment or bullying of any sort, at any level.''

Current artistic director, Matthew Warchus, sent his ''genuine and deep sympathy'' to the alleged victims but dismissed claims by some ex-employees that the 58-year-old actor's actions had been an open secret at the theatre.

He said: ''I have genuine and deep sympathy for all those who have come forward and said they were hurt in some way by my predecessor's actions. Everyone is entitled to work in an environment free from harassment and intimidation.

''These allegations have been a shock and a disturbing surprise to many of us. It is incorrect, unfair and irresponsible to say that everybody knew.''

Of the 20 testimonies, all but two incidents were said to have occurred before 2009 and just one had previously made a complaint.

The Old Vic also stressed that ''no legal claims, formal grievances, formal disputes, settlement agreements or payments made or authorised were made at all in relation to Kevin Spacey during his tenure''.

The 'American Beauty' actor has yet to comment on the allegations against him.