Thousands of suspects under investigation for violent and sexual offences have been released without condition since a 28-day limit on police bail was introduced a year ago.
In one three-month period, 12 forces released more than 3,000 violent crime, murder, rape and sexual offences suspects, figures seen by the BBC show.
A police watchdog previously warned this could endanger vulnerable victims.
The Home Office said it had asked forces to review their use of bail.
Under the new measures, which were introduced in England and Wales last April, bail should only be used when deemed “necessary and proportionate” and must be limited to 28 days.
Extensions of up to three months must be authorised by a senior police officer, and longer periods only granted by a court in exceptional circumstances.
The changes were brought in to stop police bailing suspects for extended periods of time without resolution, following a series of high-profile cases.
The figures for April to June 2017, disclosed to the BBC under a Freedom of Information (FOI) request, reveal the number of suspects bailed has fallen by two-thirds since the restrictions came into force.
Among the suspects released were 1,692 people arrested for violent crimes, 768 rape suspects and 31 questioned on suspicion of murder.
Pre-charge bail is when police release an arrested suspect but continue their investigation before deciding whether to charge them.
Suspects who are still subject to police inquiries but spared bail conditions are released “under investigation” – without a date to report back to authorities.
The BBC contacted the 43 forces in England and Wales to find out how many people suspected of violent and sexual offences had been released in this way.
The 12 constabularies who provided data were Bedfordshire, Cumbria, Derbyshire, Devon and Cornwall, Kent, Leicestershire, Merseyside, Northamptonshire, Surrey, Warwickshire, West Mercia and West Yorkshire.