Magistrates are warning that government plans to close as many as a quarter of London's courts could undermine public confidence in the capital's justice system.

The Magistrates' Association says witnesses, defendants and court staff could be forced to travel excessive distances and communities would be deprived of a "basic" service.

A blueprint by Her Majesty's Courts Service suggests that up to nine magistrates' courts could be closed.

It says the capital's 32 magistrates' courts, which only need to open for five hours a day to qualify as fully operational, are in action for just 77 per cent of this time. The number of the courts should be significantly reduced over the next 10 years to a "much smaller core", it says, conceding that this could leave some boroughs without a court.

"Geographical proximity" should no longer be the "primary factor". It adds: "Almost one in four courtrooms could be closed without detriment to timeliness or effectiveness of trials."

There is no indication which courts might close, but figures show among those with the lowest usage are Sutton, operating at 44.2 per cent of capacity, Brent at 52.4 per cent, Acton at 52.7 per cent and Bromley at 57.8 per cent.

The document says "quality and efficiency" should be more important in future. It adds: "Resources are being stretched. Many courts are struggling to provide effective services."

John Howson, the deputy chairman of the Magistrates' Association, criticised the idea of a "heavily centralised system of mega-courts". Some people already have to travel more than an hour to their local court, he said.

He added: "Many who find themselves in our courts are neither the most wealthy nor adaptable in society. A justice system that fails to take this into account risks losing the confidence of a large section of society."

One reason for the low usage was that cases were being dealt with more quickly, he said. "It would be a real irony if that success, along with a reduction in crime rates, were to deprive many communities of a basic service."