Police investigations into more than half of all crimes reported in London are dropped at an early stage, the Standard reveals today.

A total of 52 per cent, or 483,943, are "screened out" if investigators believe there is little chance of solving them. The most likely cases to be dropped are burglaries and theft.

Scotland Yard says there is always a "primary investigation" into reports of offences.

This can involve a visit and an interview with a police officer, or merely an interview with a phone operator or a civilian manning the front desk of a police station.

Nearly all serious crimes including murder, serious assaults, sex assaults, arson and hate crime, are automatically investigated. Muggings are also nearly always looked at.

However, nearly two thirds of burglaries reported to police are dropped, while theft offences are least likely to be investigated with 76 per cent of cases shelved.

Police say screening has been taking place for years and is vital to ensure that resources are deployed efficiently. However, it was criticised by London Assembly Green Party member Jenny Jones. She said: "Screening crimes is short-term gain at the cost of long-term pain. It seems like a sensible approach but the result can be a long-term rise in particular types of criminal behaviour.

"London's lawless roads are a direct result of the Met policy of deliberately neglecting minor traffic offences. By having a policy which discourages local police from asking drivers for their insurance and licence, we created a situation where a fifth of casualties involve a hit and run driver." She called for the Met to shift resources away from public order and anti-terrorist activities back into main street crime.

Scotland Yard's detection rate for burglary ran at just 16 per cent in the last financial year. Out of the total 921,779 crimes recorded by the Met between April last year and March, 196,504 were recorded as "detected" - a rate of 21.3 per cent. The figures for the same period also show that 70 per cent of criminal damage cases are dropped.

Most offences involving sex and violence are pursued though a significant minority of these cases - 15 per cent - are shelved.

The figures, contained in a police study to go before members of the Metropolitan Police Authority tomor row, s ays crimes are "screened out" when there is no forensic evidence and no obvious leads such as a description of the suspect or of a vehicle involved. Police emphasise that "screening out" offences does not mean that they are ignored. Analysts use all offences when "mapping" crimes and examine all crimes when looking for possible linked cases which can then lead to a suspect's arrest.

The study by Detective Superintendent David Way admits there are advantages and disadvantages of crime screening. He says: "The increased time available for investigators to solve screened-in crime does result in a better service for these victims.

"However it can be difficult for victims of screened out crime to understand why no further active investigation will take place. This can lead to a feeling that 'police did nothing about it'."

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