Oliver Letwin has dismissed a ministerial visit to a London police drugs unit as "a gimmick".

The attack came as Home Office minister Hazel Blears met officers at Haringey police station, where she highlighted a £46.2 million government package aimed at reducing drug-related crime in the 30 worst-affected areas in Britain.

The scheme began in April and includes compulsory drugs testing, community sentences and access to treatment advice on arrest.

"Drug testing helps the police to identify drug users who are committing crimes to fund their habit, therefore opening a path into treatment away from a life of crime," said the minister.

"The percentage of offenders testing positive - as high as 66 per cent of those tested in the Hackney pilot and 47 per cent in Haringey in the first month of testing - show that we are right to target this group of offenders.

"With the right treatment and support in place to get them over their addiction we can reduce crime dramatically in these areas."

However, the shadow home secretary accused Blears of "headline-grabbing" ahead of her meeting.

"This government specialises in using photo opportunities and gimmicks to disguise the fact that it has utterly failed to introduce a coherent drugs strategy," Letwin said.

"Another day, another headline-grabbing visit. Perhaps Hazel Blears could explain during her visit why drug offences in Haringey have risen by 23 per cent in the last 12 months, and doubled since 2000."