Brand called Sachs' mobile four times during his show
The BBC has apologised to actor Andrew Sachs for the "unacceptable and offensive" content of calls made to him by Russell Brand during a radio show.
The Fawlty Towers star was called four times during a prank on Brand's BBC Radio 2 show on 18 October.
The actor's agent said Sachs was "very upset" after Brand and guest Jonathan Ross left lewd messages about the actor's granddaughter on his voicemail.
Brand himself apologised for the offence on his latest show.
He said "you musn't swear on someone's answer phone", but added it was "funny".
A BBC Radio 2 spokeswoman said: "We have received a letter of a complaint from Mr Sachs' agent and would like to sincerely apologise to Mr Sachs for the offence caused.
"We recognise that some of the content broadcast was unacceptable and offensive.
She added: "We are reviewing how this came about and are responding to Mr Sachs personally. We also apologise to listeners for any offence caused."
Brand and Ross speak after the show
Sachs, who played Manuel in Fawlty Towers, was expected to be a guest on the programme, but was unable to appear due to unforeseen circumstances.
Brand and Ross went on to leave a series of messages on the 78-year-old's voicemail during the two-hour radio show, which included obscene comments about Sachs' 23-year-old granddaughter.
In the first message, Ross suddenly swore and said Brand had slept with her.
He then apologised and said he "got excited".
Later in the programme, Brand said the only way to rectify the incident was to make another call - but caused further offence after he suggested Sachs might kill himself because of the previous message's revelations.
A third call saw Brand and Ross singing an apology to the actor.
Brand sang: "I'd like to apologise for the terrible attacks, Andrew Sachs. I said some things I didn't have oughta [sic], like I had sex with your granddaughter."
During the fourth call, Brand said: "Now when I watch Fawlty Towers I think I'm going to think I've hurt his feelings."
Andrew Sachs was unable to answer Brand's calls
A BBC spokeswoman said the programme had received two complaints related to Ross's swearing - rather than the content of the phone calls - before details of the incident were publicised in a Sunday newspaper.
A further 1585 further complaints have arrived since.
Sachs' agent, Meg Poole, has written a letter to Radio 2 controller Lesley Douglas asking for an unreserved apology.
Ms Poole told BBC News that the actor had passed on his mobile phone number to Brand's production team "in good faith", which the presenter used to contact him during the show.
She added that the actor did not hear the programme, but listened to a recording and was "offended very much indeed" by its content.
Talk show host and Radio 2 presenter Jonathan Ross has now sent a personal apology to the actor and it is understood Brand is planning to do the same.
Earlier this year, Brand apologised for making a hoax call to the police during a stage show in Northampton.
He rang a police line in front of an audience and said he may have spotted a man who was responsible for a series of assaults.
Brand later said he was "devastated by the possibility" that he "may have offended vulnerable people".
The 33-year-old star, who hosted the MTV Music Awards in Los Angeles last month, has been a regular presenter on Radio 2 for almost two years.
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