A scheme to prevent children accessing pornography, gambling and other adult services on the latest mobile phones is to be reviewed by the telecoms regulator.

The inquiry has been triggered by complaints from charities about the project, which was launched at the request of the Home Office. It could lead to the voluntary code being replaced with tough new rules.

Mobile phone networks including Orange, O2 and Vodafone signed up in 2004 to a code that is aimed at protecting children using “next generation” 3G phones that offer services including internet access, video cameras and full-colour screens.

Under the code, the phone companies agreed to offer parents who bought the 3G models for their children the ability to install a filter, which would block access to unsuitable internet content such as adult chatrooms.

A classification system for content — similar to that used in cinemas — was also introduced, with unsuitable material to be labelled “18”.

The phone companies also agreed to work with law enforcement agencies on the reporting of potentially illegal material.

However, children's charities fear that some of the mobile operators have been lax about marketing and getting to grips with the scheme.

John Carr, secretary of the Children's Charities' Coalition for Internet Safety (CHIS), an umbrella group that includes NCH, Barnardos and The Children's Society, said: “My guess is that not all the networks are doing equally well. We have done our own informal studies in some mobile phone shops, where some shop assistants do no know elementary stuff about internet safety.”

A spokesman for Ofcom said: “To ensure that children continue to receive appropriate protection, Ofcom is working with the CHIS and the mobile operators to review the voluntary code of conduct for mobile content.” A report is expected in the summer.

Mobile phone ownership among the young is common, with a million under-10s in the UK — one in three — now owning one, according to figures from mobileYouth, a research consultancy.

Separate figures from Ofcom found that 32 per cent of children aged 8-11 regularly use a mobile.

The access that the latest phones provide to the internet — often away from parental supervision — was cited last year as an increasing concern in a report by the Child Exploitation and Online Protection Centre, a branch of the Serious Organised Crime Agency, which is dedicated to combating child abuse.

The report concluded that the boom of phone ownership among under-18s had created an “increasing opportunity for the sexual exploitation of children and young people”.

A particular concern, it said, was the growth of use in mobile social networking sites via mobile phones.

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