World heritage authority Unesco is closely following developments in the case of the eight-storey extension to the judiciary chambers which has been highly criticised for marring Valletta’s skyline.

It will be contacting the Maltese government for “information and comments”, a Unesco spokesman has told The Times.

Valletta enjoys Unesco world heritage status. The building in Strait Street has been slammed by heritage groups because the extra floors tower over the surrounding buildings and the Chamber of Architects has questioned if it might compromise the city’s status.

Commissioned by the government, the €1.8 million project involved joining two adjacent houses and raising the floors to eight to accommodate the judiciary chambers and the family court. The development is in line with planning authority permits.

Junaid Sorosh-Wali, from Unesco’s World Heritage Centre, said it had not yet received any complaints about the government project.

However, following The Times’ questions, Mr Sorosh-Wali said he was passing on the information to Icomos International – Unesco’s advisory body on cultural sites – and to the “competent national authorities for information and comments”.

Ray Bondin, Malta’s Ambassador to Unesco, said “as yet, nothing has been received in Malta”.

He explained that any complaints that reach the Unesco World Heritage Centre were passed on to the state, in this case Malta, for a reply and to Icomos.

“If following these responses, Unesco feels there is a need for more information, normally, an inspector is then sent to visit the site and meet the authorities,” Mr Bondin explained.

Each country with a listed heritage site has a “responsibility” to inform the centre of any project that might affect the outstanding universal value of a World Heritage Property, Mr Sorosh-Wali said.

According to heritage operational guidelines, “the World Heritage Committee invites the state parties to the convention to inform... of their intention to undertake or to authorise in an area protected under the convention major restorations or new constructions which may affect the Outstanding Universal Value of the property”.

The guidelines also state that “notice should be given as soon as possible (for instance, before drafting basic documents for specific projects) and before making any decisions that would be difficult to reverse, so the committee may assist in seeking appropriate solutions to ensure the Outstanding Universal Value of the property is fully preserved”.

Once the committee receives comments about a specific project – including the potential heritage impact assessment – it analyses the information and issues its recommendations.

“Most of the potential problems are solved during this bilateral consultation process,” Mr Sorosh-Wali said.

A World Heritage property is delisted by the committee if it loses its “outstanding universal value” after a long process of monitoring and assessment.

So far, only two properties throughout the world have been removed from the World Heritage List, he added.