Nearly all criminal law practitioners have encountered a failure to disclose evidence in the past 12 months, according to a survey which attracted over 1,200 responses.

The BBC commissioned a survey in conjunction with the Criminal Law Solicitors' Association, the London Criminal Courts Solicitors' Association and the Criminal Bar Association. Its results will be broadcast tonight. 

According to the findings, 97% of respondents said they had encountered disclosure of evidence failings in the past 12 months. More than half (55%) encountered these problems every day or every week. The failures were evenly split as occurring with the CPS or police. or At least four in 10 practitioners encountered a disclosure failure in the magistrates' court, 45% were encountered in the Crown court. Nearly eight in 10 said failures had delayed the trial. More than eight in 10 said the failures put the defence under unreasonable logistical or time pressure. Over half (56%) said the failures caused a case to collapse. A third said the failures resulted in 'possible wrongful conviction or miscarriage of justice'. 

Disclosure failings have made national headlines since a rape trial involving student Liam Allan was abandoned following the discovery of crucial text message evidence that had not been disclosed to the defence. The police and CPS apologised to Allan in January.

The CLSA said the results would not surprise those who do regular criminal work but acknowledged that the findings will shock those 'who still maintain there isn't a problem and everything in the disclosure garden is rosy'.

The association added: 'We hope we can persuade the government and judiciary to take urgent steps to tackle these ongoing breaches of the existing rules and certainly hope that once the dust has settled, we can work together with the relevant parties to reform the system so that we do not experience these very frustrating day-to-day issues with disclosure and so that the public can have confidence that the system is treating all parties fairly and securing justice for those involved.'

The Commons justice select committee has begun an inquiry into the disclosure of evidence in criminal cases. The Law Society wants to hear from solicitors about failures that have or could have led to miscarriages of justice. Case studies should be emailed to the Society by 9 March.

The practitioner groups' findings will feature on File on 4, a current affairs programme, on BBC Radio 4 at 8pm today.