Kevin Spacey has been accused of sexual harassment by 20 people during his time at The Old Vic.

The theatre, one of Britain's major theatrical institutions, originally said no complaints had been made against the actor when allegations first came to light last month.

But bosses today admitted the complaints had been made about the Hollywood star to a hotline set up by the theatre in the wake of the scandal.

Spacey was artistic director at the theatre for 11 years from 2004.

A statement from The Old Vic said: 'The investigation resulted in 20 personal testimonies shared of alleged inappropriate behaviour carried out by Kevin Spacey during his time as Artistic Director.

'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.

Shamed: Kevin Spacey has been accused of twenty incidents of sexual abuse and inappropriate behaviour while at the Old Vic, it was disclosed today

Complaints: A hotline set up by the theatre where he was artistic director for 11 years has received twenty complains after he admitted he had acted sexually against a schoolboy actor

The theatre's CEO Sally Greene has aplogised for Spacey's menace, but denied she or any of her staff had the activity reported to them until recently.

Ms Greene, who brought Spacey to the London theatre in 2004, said that she was 'sick to the stomach' at the allegations of sexual abuse against Spacey.

Ms Greene, 56, said the allegations made against Spacey 'have shocked and appalled me, and everyone who works within the entertainment and arts industry.'

It was revealed that one person came forward at the time they were claiming they were abused by Spacey, but no action was taken. The other 19 are fresh allegations.

Spacey's status as an international star ensured he was allowed to continue his alleged abuses without being uncovered, it was said.

Top law firm Lewis Silkin were deployed by the Old Vic on October 31 to probe the menacing reign of Spacey at the theatre.

'This investigation concluded that there have been 20 personal allegations of incidents relating to The Old Vic ranging from 1995 to 2013, with the majority (all but two) falling before 2009' the theatre said.

'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.

'Shocked and appalled': Sally Greene, chief executive of The Old Vic Theatre, said she felt 'sick to her stomach' at claims of sexual misconduct made against Hollywood star Kevin Spacey

Spacey's status as an international star ensured he was allowed to continue his alleged abuses without being uncovered, it was said

Showpiece: The theatre, one of Britain's major theatrical institutions, was reeling after the number rose since the email address to register complains was set up last month

'It has also not been possible to verify any of these allegations, and it is important to note that Kevin Spacey has not commented on them.'

'The given testimony shows that in all but one case, those individuals alleging inappropriate behaviour by Kevin Spacey did not come forward at the time or asked that no formal action be taken.

'During his tenure, The Old Vic was in a unique position of having a Hollywood star at the helm around whom existed a cult of personality. The investigation found that his stardom and status at The Old Vic may have prevented people, and in particular junior staff or young actors, from feeling that they could speak up or raise a hand for help.

The Old Vic is deeply dismayed by the allegations and thankful to all those who have contacted its helpline directly. Without them it would not have been possible to conduct such a thorough review.

'With the exception of one of the claims, none of the reported incidents were raised formally or informally with management.

'Staff who observed this behaviour claimed they were unclear about how to respond; in some cases they did not consider allegations of misconduct to be serious and, where they clearly did, they said they did not feel confident that The Old Vic would take those allegations seriously given who he was.

Fallen: Spacey, who won an Oscar for American Beauty, was artistic director at the theatre for 11 years from 2004

'The following factors may have contributed to this escalation problem: star power; lack of clarity of The Old Vic's accepted code of behaviour; confusion regarding the impact of reporting misconduct; career insecurity; tribalism between operational and creative staff during his tenure causing information gaps.

'Calling out this behaviour could have been easier if there had been a non-formal and confidential mechanism in place by which complaints could be raised safely within the organization.'

The theatre said it would be installing a plan for staff to report any future abuses and appoint 'Guardians' to look after young actors and other staff at the theatre as part of a new safety network.

'For those who were affected during Kevin's tenure, our victim support counselling service will continue to be open 24 hours a day, 365 days a year for the next 12 months. We hope this goes some way towards providing a support structure for those affected, together with the knowledge that the testimonies they have shared will help inform the way forward at The Old Vic and in the wider industry.

Nick Clarry, Old Vic chairman said: 'On behalf of The Old Vic Board of Trustees, to all those people who felt unable to speak up at the time, The Old Vic truly apologises. Inappropriate behaviour by anyone working at The Old Vic is completely unacceptable.

Ms Greene (pictured with Spacey and Elton John in 2003) said she had no prior knowledge of concerns regarding his behaviour and would never have appointed him had she known

'We will foster a safe and supportive environment without prejudice, harassment or bullying of any sort, at any level. We want anyone who works here to feel confident, valued and proud to be part of The Old Vic family.'

The theatre's artistic director Matthew Warchus 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.

'The Old Vic is now actively engaged in the process of healing and the process of prevention.

'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. But as a result of the investigation, what we have learnt is how better to call out this behaviour in future.

These findings will help not only The Old Vic but our industry as a whole, as together we rapidly evolve an intelligent new standard of protection and support in and around the workplace. We are committed to a new way forward.'

Actor Anthony Rapp, best known for his role in Star Trek: Discovery, claimed Spacey made sexual advances to him when he was a 14-year-old boy.

But the Old Vic was adamant today that none of the twenty complainants were minors when they alleged they were Spacey victims.