A £3 million artificial reef at a coastal resort is producing waves that are too short and too difficult for the average surfing enthusiast, according to a report.

The man-made reef at Boscombe, near Bournemouth, was the first of its kind in the northern hemisphere but has had a mixed reaction from surfers.

Now the council is withholding a £150,000 performance payment from its creator, ASR Ltd, until the issues are resolved.

Problems identified in a study published today include issues with the length of ride and the frequency of waves, while the waves themselves need to be "slightly less challenging" to attract journeyman surfers.

The findings were based on a performance assessment by experts at Plymouth University showing the reef had only achieved four of its 11 objectives since opening in November.

Created some 225m out to sea and made of 55 sand-filled bags, the reef was aimed at making surfing conditions better.

Bournemouth Borough Council's summary of the report found that: "The reef does work and, in the right conditions, is producing steep, challenging waves suitable for expert surfers.

"But the ride is not as long as required; frequency of surfing waves is not as often as (those on) the beach; and the wave would be surfable by more people (intermediate as well as expert surfers) if it were slightly less challenging.

"The current assessment reflects a combined view of Plymouth University, council officers and representatives of the local surfing community. This assessment has also been agreed with the contractor, ASR Ltd."

The information was partly garnered from cameras monitoring the breaking waves' shape and strength.

Mark Davidson, of the university's School of Marine Science and Engineering, said today: "The results of this analysis showed that the reef was successful in producing a new wave at Boscombe which was rideable for experienced surfers and boogie-boarders.