Documents have revealed the decaying state of the Burrell Gallery in Glasgow, which hosts one of Scotland’s most treasured art collections.

So much water is seeping into the 32-year-old building’s roof, “significant vegetation growth” has been found in ceilings.

The building has been declared “not fit for purpose”.

The disclosures come after Glasgow Life, which runs the city's museums and galleries, provided a file of documents under Freedom of Information legislation.

They show that a planned £66 million renovation - three times the original cost of the building – is falling £15 million short of its target, with officials warning that inflation will push this figure up.

An application for cash to the Heritage Lottery Fund by Glasgow Life, the body which runs the Burrell, explains: “Over the last 30 years, a range of serious problems has arisen with the Burrell Collection due to its original design and construction. The building is no longer fit for purpose: water ingress through the roof threatens the collection.... Temporary roof repairs have regularly been undertaken to alleviate the water ingress and tarpaulins, plastic sheeting and drip buckets have been used internally to manage its impact…."

Other documents flag up the discovery of “significant vegetation growth” in the roof space, while the glazing on the north face of the building has been attacked by algae.

Papers state: “Water is finding its way into the building through the roof, roof lights and glazing.

“The design of the roof was ill-conceived from the outset.”

A spokesman for Glasgow Life said:“This is a major capital project, which involves significant amounts of planning and procurement - it’s important to get that in place before announcing any date for work to begin.

“The building which houses the collection was at the cutting edge of both design and technology when it was built. Unfortunately, some of those designs did not stand the test of time and much of the fabric of the building requires replacement.

“We would never allow for any danger to the collection, hence the reason why some galleries are already closed due to water ingress.”