Detainees are being held in handcuffs for too long and too many are being strip-searched in Tower Hamlets police custody, a report by the prisons regulatory body said.

Police chiefs in charge of the two custody suites at Bethnal Green and Limehouse stations were criticised for the “lack of appropriate monitoring of the use of force” in the probe by HM Inspectorate of Prisons.

But the investigation added that facilities had been “much improved” since the last study in 2009.

Among the worse examples was that of a 15-year-old schoolboy, brought to Bethnal Green station after being arrested for a minor offence.

The report said: “He remained handcuffed, with his hands behind his back, in the waiting area for approximately 45 minutes before being booked in, even though he was compliant. Despite the prompt attendance of his mother, he was kept in a cell for several hours before being interviewed.”

Guidelines state handcuffs “should only be used when necessary, justifiable and proportionate” and “should be removed as soon as possible” once in custody.

Investigators also found there was a lack of facilities provided by Tower Hamlets council, leading to “some juveniles being unnecessarily detained in police custody overnight”.

If a child aged 10 to 16 is charged and denied bail they should be transferred to the local authority.

Police were, however, praised for recently appointing a custody manager and the report added that cells were generally clean.

Nick Hardwick, chief inspector of prisons, and Dru Sharpling, HM inspector of constabulary, said: “Healthcare services had improved greatly; the recruitment of nurses having a positive impact.”

Supt Rob Revill, acting borough commander for Tower Hamlets police, said the high number of strip searches were down to drug prevalence.

He explained: “They haven’t looked at the nature of the borough There’s a drug problem so searches will be high.”

A lack of council accommodation for charged juveniles is a “country-wide problem”, he added.

Mr Revill said: “I’m happy that we’ve driven through improvements. We will monitor the use of handcuffs in the future.”

From January last year to November the two custody suites – 19 cells at Bethnal Green and seven at Limehouse - held almost 8,700 detainees.