Police faced further questions over sex cases today after another rape trial collapsed when evidence undermining the accuser's claims came to light at the eleventh hour.

Christopher Penniall was cleared after messages which suggested his victim consented to a 'one-night stand' were obtained at the request of his defence.

Prosecutors dropped the case against him at Woolwich Crown Court as the judge highlighted the importance of telephone downloads which could undermine the accuser's case.

A rape case at Woolwich Crown Court is the latest to collapse amid concerns over disclosure

Mr Penniall, 43, had spent 16 months with the case hanging over him on bail, after handing over his Facebook details which he said contained messages which supported his insistence that the woman agreed to sex, The Times reported.

The paper reported that the woman had deleted the messages and police only downloaded them days before Mr Penniall's trial, following a request by the defence.

After the case collapsed this week, Judge Christopher Kinch told the court: 'This case just highlights the importance of the police pursuing full telephone downloads where they are clearly central to the allegations being made and the defence being made.'

Judge Christopher Kinch said the case shows the importance of accusers phone records being examined by police

London's Met Police Commissioner Cressida Dick today defended her officers against criticism over the issue.

She told LBC radio: 'This is something that's causing I know, the public a lot of concern, not just in London, but beyond. [It's] something I'm taking very seriously indeed. I'd like to say that I'm absolutely clear, my officers do act fairly, they do act impartially.

'I have seen no sign whatsoever of anything failing to be disclosed as a result of malice or ill will. It is a very, very complicated system that we're working in and there are, as you've probably read, ever increasing amounts of digital media that the officers have to look at.'

Last week, the Metropolitan Police and prosecutors were forced to apologise for a litany of blunders which led to student Liam Allan being wrongly accused of rape.

Mr Allan, a criminology student at Greenwich University in London, spent two years on bail accused of rape and sexual assault.

Metropolitan Police Commissioner Cressida Dick today insisted officers do act fairly

Mr Allan's case collapsed last December, sparking a national row over the failures by the authorities to disclose relevant information to defendants.

The messages sent by the woman in that case included one to a friend saying: 'It wasn't against my will or anything.'

Others read: 'Sometimes sex is the number 1 priority, I'm really not joking to be honest,' and, 'You know it's always nice to be sexually assaulted without breaking the law.'

Scotland Yard is now reviewing 600 cases of rape and sexual assault which are awaiting trial, with thousands more under review nationally, the CPS has said.