Roman Polanski's lawyers have filed an appeal over alleged judicial misconduct in his 1970s child sex trial in the US.

The appeal cites new evidence that a prosecutor was aware of misconduct by the judge handling the case in 1977.

Polanski has been under house arrest in Switzerland since September facing a US arrest warrant over his conviction for unlawful sex with a 13-year-old girl.

The 76-year-old director left the US in 1978 before he could be sentenced and has never returned.

'Secret testimony'

The appeal - asking that a special counsel investigate alleged judicial misconduct - was filed on Thursday at Los Angeles Superior Court.

Polanski's lawyers say former Deputy District Attorney Roger Gunson gave secret testimony this year on the judge's conduct.

They asked that the transcripts of Mr Gunson's testimony be unsealed. They also asked that Polanski be sentenced to time served without requiring his presence in court.

In January, a judge in Los Angeles ruled that Polanski must appear in court in the US before he can be sentenced.

Switzerland has said it will not decide whether to extradite the director until any appeal over his US trial is resolved.

The Swiss justice ministry has said it would make "no sense" to move him from house arrest before a definitive ruling in the US.

Polanski's latest film, The Ghost Writer, won the Silver Bear award for best director at the Berlin Film Festival in February.