The city-wide 20mph zone in Portsmouth is being extended today in phase 2 of the scheme. Safe Speed says this is a useless and misguided scheme that is likely to reduce safety.

Paul Smith, founder of SafeSpeed.org.uk, said: "It's terribly important to road safety that we get vehicle travelling at appropriate speeds. But appropriate speeds are never determined by numbers on signs. Appropriate speeds are only determined by drivers adjusting their speed to suit the immediate conditions."

"We're shifting the balance from responsibility to regulation and it simply does not work. We need more responsibility, not more regulation."

"Latest national figures indicate that average accident severity is far higher in 20mph zones than in 30mph zones."

* In 20mph zones in 2006 17% of injury crashes were fatal or serious* In 30mph zones in 2006 13% of injury crashes were fatal or serious

"We are extremely worried by these figures, and until we know exactly why this is happening no further 20mph zones should be rolled out."

"The scheme is useless and misguided. It will very likely cost lives."