Cases of babies being shaken have often been given low priority by senior police officers or have been regarded as too difficult to prosecute.

According to the report, drawn up by two Scotland Yard detectives, police and lawyers have failed to recognise that they have often been dealing with murder or attempted murder and would need highly skilled forensic and medical aid. When police called a national conference of 150 detectives last year to discuss shaken babies only seven officers had received any training, yet 41 had actually carried out investigations.

Although shaken baby cases are among the most complex to investigate, few senior officers were prepared to commit manpower. When the authors of the study examined one case they found it was being investigated by a lone sergeant equipped with a box file.

If a case went ahead, police faced juries unwilling to accept the possibility that any parent could harm their baby. The report said: “This lack of belief that parents and carers could stoop to such a crime is one of the major difficulties police have in convincing juries.”

Even if attackers were successfully convicted the study found that penalties by courts were inconsistent, ranging from a suspended sentence to life imprisonment.

When a baby is violently shaken, causing its head to whip backwards and forwards, the brain moves within the skull breaking blood vessels and leading to a blood clot.

The latest Home Office crime figures for 2000-01 show that children under the age of one are the group most at risk from murder. Some 70 per cent of offenders are men.

Detective Chief Inspector Phil Wheeler, co-author of the report, said that his research suggested there were at least 200 cases a year. Only last week Mr Wheeler, now a national expert on the crime, was contacted about four new cases across the country.

He said: “People don’t realise the number of cases. We fall down because people say it’s a baby and the child protection team can deal with it, not a murder squad.

“We don’t recognise the child is as important as the adult,” he added. There would be a public outcry if people realised the extent of offences. When Mr Wheeler, who carried out the successful prosecution of the Australian nanny Louise Sullivan in 1999, started his research he found that many officers began investigations by desperately searching round the country for a colleague with any experience.

The researchers found a London case from 1992 in which the baby survived but the Crown Prosecution Service decided against prosecuting the father although there was evidence of abuse. The police had collected five statements. The Louise Sullivan case needed more than 100 witnesses, including 56 doctors.

The report noted: “The police service is probably at its best investigating murders of children who are somewhat older than one year of age. In making visits to police officers who are investigating cases, it is clear that the death of a baby is given second-class status by senior officers.”

Computers and manpower are not available and detectives are left to rely on old-fashioned methods. Yet they need highly skilled medical advice and evidence to counter clever defence lawyers.

Mr Wheeler said one of the problems was the lack of experts such as paediatric and ophthalmic pathologists. “There are cases where people are getting away with it,” he said.

Cases were not going to court because of the difficulties of putting a time to when attacks took place and ascertaining the perpetrator of the assaults. Defence lawyers would sometimes claim the injuries came after a child had rolled off a sofa or as a reaction to vaccination.

But Mr Wheeler said that recent research had led to improvements by police, and investigations had become better. A thousand CDs giving details of how to investigate shaken baby cases were being sent by the Home Office to police.

The 230-page report ends with 29 recommendations, including a requirement for police to send details of all cases to the Department of Health and that everyone handling shaken baby cases should be given special training.

The report calls for the reorganisation of the management of child protection units across the country. It also advocates widely distributed publicity that would issue warnings of the dangers of shaking babies. The publicity should be aimed particularly at men aged between 18 and 25.