Scotland Yard is urgently reviewing 30 rape cases that are about to go to trial amid fears police blunders could cause them to collapse.

The Metropolitan Police ordered a review of all current sex abuse investigations after two prosecutions collapsed within days because the police withheld vital evidence.

In both cases, a detective in the force's Child Abuse and Sexual Offences (Caso) unit failed to disclose material that could have assisted the defence team.

It is now feared scores of other rape and sex abuse cases could be thrown out due to problems around the way detectives have handled the disclosure of material.

Commander Richard Smith, who oversees rape cases for the Met, said the review would prioritise around 30 live cases that are about to go to trial.

Dozens of others, in which the suspect has been charged and is waiting for the court process to begin, are also to be re-examined.

Mr Smith said: "The review is into all current investigations where someone has been charged. Thirty cases that are about to go to trial and they are our priority."

It comes amid warnings that police are making basic errors in their desperation to improve conviction rates in sex abuse cases. Currently, 11.2 per cent of rape allegations result in a conviction.