Work on a multi-million pound hospital expansion has been delayed because the cost will be higher than originally thought.

Work was due to start at the beginning of this month on the £4.6 million scheme at Mill View Hospital in Hove.

But work is now on hold after South Downs Health NHS Trust, which owns the hospital, discovered the project could cost hundreds of thousands of pounds more than originally estimated.

The extra costs are believed to include unforeseen needs for more building materials and supplies.

The hospital, which was opened in 1998, provides inpatient, outpatient and day patient care to people under 65 with mental health problems in Brighton and Hove and Lewes.

The proposed expansion will eventually provide two new ward areas with single rooms for up to 35 mental health patients currently at the trust's Westbourne Hospital in New Church Road.

The patients were transferred there from the Freshfield mental health unit at Brighton General Hospital last year because the conditions of the wards there were inadequate.

They were placed at Westbourne temporarily until the new unit opened.

The delay means the planned opening date of the unit in 2002 is at risk.

The trust is now looking at ways to make savings to recoup the extra costs and to speed up work.

A spokesman said: "We are in negotiations with the contractor to see where any cutbacks could be made without reducing the quality of the expansion plans.

"We are also doing a savings exercise to see where other cuts in costs can be found, such as with supplies of materials.

"It is not unusual for a trust to be in this position because we have to make an original estimate at an early stage but often unexpected extra costs can come in.

"There is no possibility of the project being at risk in any way but there is going to be a delay before work is going to start."