The government has insisted that closed circuit TV cameras help to cut crime, despite research suggesting they have limited impact.

Home Office statistics show crime fell in 13 of the 24 cases studied after CCTV cameras were installed but crime rates rose significantly in four others.

Home Office Minister Lord Falconer believes the cameras have had a "significant" impact on crime levels where they were properly used and maintained.

The findings are published on the day a closed circuit television system described as the UK's largest and most advanced was switched on in Manchester.

In terms of providing people both with security and a sense of security, this is a good investment

Lord Falconer, Home Office Minister

That �3m operation uses digital technology to cover the whole of the city centre with 400 cameras.

Lord Falconer, who unveiled the Manchester scheme on Friday, said the technology would help in the battle against street crime.

CCTV had no effect in seven of the 24 schemes being monitored, according to a report by the National Association for the Care and Resettlement of Offenders (Nacro) into Home Office research

The schemes included ones in town centres, housing estates, public transport and car parks.

Manchester scheme

Lord Falconer said that despite the Nacro findings, CCTV helped people feel safer.

He said: "They help the police in both apprehending people they wish to interview and all of us have seen examples over the last few weeks and months of CCTV cameras helping to apprehend such people, and they also help to secure convictions in court.

"In terms of providing people both with security and a sense of security, this is a good investment."

The Manchester scheme aims to cut crime

He conceded that more research was needed into the use of CCTV.

Nacro warned against over-investing in the cameras at the expense of "more effective measures" such as street lights.

Rachel Armitage, of its crime and social policy unit, said: "It would be foolish to claim that well planned CCTV can never have an impact but the effectiveness of CCTV is often overstated."

The Manchester CCTV scheme is the largest single security camera project controlled from one centre in the country.

Councillor Kath Robinson, deputy leader of Manchester City Council, said: "This fantastic new facility will allow us to continue to protect individuals and stakeholders and their peaceful enjoyment of our magnificent city centre."

The project has been piloted since last February but will now be fully operational.