The cost of building Aberdeen's new Museums Collections Centre has soared by £3m, it has emerged.

The facility in Northfield was expected to open in late 2014 and cost £3m but a series of delays have pushed the cost up to around £6m.

Named the Aberdeen Treasure Hub by local school pupils, the centre will not open until at least July.

It will house hundreds of publicly-owned works of art which are not normally on display - thought to be about 90% of the city's collection.

The council set aside £3m to build the facility in November 2012 on the understanding that it would be completed in December 2014.

It was expected to be ready to store the city's collection when Aberdeen Art Gallery closed for a £30m revamp in early 2015.

By March 2014, the completion date had been pushed back to April 2015 as the local authority still had not chosen a builder.

The Robertson Group won the contract in December 2014 but by this time the anticipated cost had risen to nearly £4m.

Ground was broken at the site in March last year, with construction then set to be completed in November 2015 at a price of almost £6m.

It is now not expected to be finished until July, less than 18 months before the Art Gallery is scheduled to reopen.

In the meantime, the city's art collection is being stored in North Lanarkshire by museum specialists Constantine.

The council originally signed a £230,000 contract with Constantine but construction delays have pushed the cost of the deal up.

Councillors were warned as far back as 2009 that the lack of an alternative storage facility could delay work on the gallery and increase costs.

Aberdeen City Council has committed £10m towards the cost of redeveloping the Art Gallery, while another £10m has been contributed by the Heritage Lottery Fund.

The local authority has underwritten the final £10m using public money, which it hopes to recover through a fundraising campaign.

A spokeswoman for the council said: "The Museums Collections Centre will house large sections of the city's collection, historical objects and art works while not on public display, but rather than just build a new storage facility the council wanted to create a site where the collection could continue to be seen.

"The contract with the storage company has been extended, with costs being met by the contingency budget."

Last month, STV News revealed the cost of restoring Aberdeen's Town House had risen by £2.3m and the work was running more than nine months late.

The local authority said the full extent of the repairs required only became clear after the restoration had begun but opposition politicians accused the council's leaders of keeping the rising cost of the project secret.

The construction of a third bridge over the River Don is also running £3m over budget and more than six months late.

It had been expected to be finished in December 2015 but now may not be completed until June.