A major museum and housing development could be delayed by fresh archaeological discoveries.

Finishing touches are being put to the plans for the new £6.6 million Chichester District Museum, which is being built on the site of the Second Century Roman baths at the Woolstaplers car park.

Experts have previously excavated around three quarters of the historic site and recovered important artefacts dating from the Roman period.

However Chichester District Council has admitted there is a risk that the work, due to start next year, could be delayed if new artefacts are found.

It could lead to spiralling costs and to the completion date, currently pencilled in for February 2010, slipping substantially.

It is hoped that a further archaeological survey of the site before the work starts will uncover any unsuspected discoveries and minimise the risks.

However the council admits it cannot rule out further discoveries once the work has begun.

A recently published council report said: "The risk of new discoveries during construction is recorded on the project risk register - the risk being delay during the construction contract which leads to increases in costs."

Numerous important archaeological discoveries, dating from various eras, were made during the recent redevelopment of the former Shippams factory site in East Street, proving the Chichester soil remains rich in history.

Most of the artefacts, which ranged from gold rings and pottery to the more recent Shippams paste pots, were put in display shortly after the work was completed.

A spokesman for English Heritage said: "There is absolutely no doubt Chichester, like many other former Roman cities, is extremely rich in heritage, the remains of which often are often still buried.

"The example of the Shippams factory is a prime example of what could still remain to be uncovered elsewhere."

The development is one of the largest ever undertaken by Chichester District Council.

Its estimated cost has already risen from an originally quoted £5 million which has been blamed on a shortage of labour due to the construction of the London 2012 Olympic Games infrastructure.

The extra cost will not fall on council taxpayers but will be met with reserves along with money from the sale of the current museum in Little London. The Roman baths are covered by a car park but will be on permanent public view when the museum is built. There are also plans to include office buildings and housing, which will bring in an extra £2 million.

Architects for the work were appointed by the council following a competitive tendering process.