A decision to extend the St John’s Co-Cathedral museum to house a collection of priceless Flemish tapestries was put on hold after an international conservation agency expressed concern at the project.

ICOMOS, a non-governmental international organisation dedicated to the conservation of the world’s monuments and sites, informed Unesco of its concerns in its evaluation report, planning authority CEO Johann Buttiġieġ told the board yesterday.

The revelation came during a board meeting discussing an application filed by the St John’s Co-Cathedral Foundation to extend the museum to build a tapestry hall.

Mr Buttigieg pointed out that the foundation could request a suspension of the application to discuss the issue with ICOMOS.

Curator Cythnia Degiorgio looked surprised and pointed out that the organisation had had the chance to send in its feedback over the past eight months. However, it was decided to suspend the application.

The project includes the extension and refurbishment of St John’s Co-Cathedral Museum. About 1,300 square metres would be built to house the museum and 200 square metres will become a Caravaggio Centre focusing on the life and works of the most celebrated artist of the Baroque era.

Architect Konrad Buhagiar, of Architecture Project, explained that the aim was to modernise the museum and properly display the stunning and priceless 29 tapestries.

The tapestry set, unique in the world, was the gift, or gioia, presented by the Aragonese Grand Master Ramon Perellos y Roccaful upon his election as Grand Master in 1697.

There is not enough space to exhibit all the pieces and these are spread through different areas of the museum.

The revamped museum will have its own entrance and exit from Merchants Street, relieving pressure from the church entrance and allowing the two to operate independently.

Mr Buhagiar explained that the museum extension would not be any higher than the surrounding buildings and would actually be lower than the structure that was bombed in the course of World War II.

Back in 2008, a nationwide debate broke out over two controversial applications filed by the foundation to extend the museum underground, beneath St John’s square, and build a three-story structure over the churchyard on Merchants Street.

These plans were dropped one year later on the recommendation of then prime minister Lawrence Gonzi and archbishop emeritus Paul Cremona.