A toilet block dating back to the first world war could be reduced to rubble if it gets in the way of the new Forth crossing.

The WC at Port Edgar, along with the adjacent air raid shelter and barracks, in South Queensferry was made a B-listed building in September last year.

Just three months later, the Scottish Government gave the final go-ahead for a new bridge.

Government agency Transport Scotland has still not finalised the detailed plans for the £4 billion bridge project and played down the threat to the old barracks.

However a spokeswoman for Historic Scotland said Scottish ministers could be asked to decide the fate of the buildings if they conflicted with the bridge proposal.

She said, “During the process of listing consultation, Historic Scotland cannot, unless there is a live application sitting with the local planning authority, take into account whether there could be possible future development proposals.

“If the proposals of a new crossing are to be considered, ultimately affecting listed buildings, then listed building consent for demolition is required which is determined by the local authority.

“If The City of Edinburgh Council is minded to give consent then Historic Scotland will assess the case for demolition and decide whether to clear the case back to the local authority or seek ministers’ agreement for call in.”

Transport Scotland reportedly tried to prevent the buildings from being listed, but the agency denied this claim.

A spokesman for Transport Scotland said, “The details of the design, land requirements and construction method associated with the proposed Forth crossing is part of the ongoing work following ministers’ decision on the form and location in December.

“Transport Scotland will always work closely with Historic Scotland and seek to avoid or, if necessary, minimise impacts on listed buildings and other designated sites where possible.

“At this stage in the development of the bridge it is too early to be specific about the range and scope of possible impacts on the barracks and how these might be addressed.”