The mosaics were at one of the world's 100 most endangered sites

The buildings, at Portsmouth Naval Base and at Carisbrooke on the Isle of Wight, are on English Heritage's 2005 Buildings at Risk Register.

Meanwhile, the Brading Roman Villa on the island has been removed from the register, published on Thursday.

Conservationists say its mosaic floors have now been protected.

Although progress is being made, some of our unique historic assets are being allowed to crumble and decay Dr Andy Brown, English Heritage

The building covering the villa has been replaced and visitor facilities upgraded at a cost of more than �3m.

The villa had also been listed by the World Monument Fund as one of the world's 100 most endangered sites before the refurbishment was carried out.

English Heritage says the Carisbrooke Romano-British villa is now classified as a "top priority at risk building".

An English Heritage fund of �3,000 had been granted to clear vegetation, which had caused damage to the building.

But the walls of the villa are still in a poor condition.

The officers' lodgings in Portsmouth, which were built between 1715 and 1719, already have Grade II* listed status.

Dr Andy Brown, regional director of English Heritage South East, said: "Although progress is being made, some of our unique historic assets are being allowed to crumble and decay."

The English Heritage Buildings at Risk Register is a list of nearly 1,430 of the nation's most vulnerable Grade I and II* buildings and monuments.