The Alexander Turnbull Library has had a big wake-up call after it bought a fake painting for $75,000, a colonial art expert says.
In 2013 the library, which collects national heritage material, bought a portrait which it believed to be by renowned painter Gottfried Lindauer.
It had been warned by colonial art expert Roger Blackley that it was a forgery hours before the sale but had ignored his advice.
Mr Blackley said there were several signs it was a fake, and he hoped the library would be more aware of forged paintings in the future.
"We also have to realise that although they do purchase works of art, generally speaking the Turnbull is the recipient of hundreds of donations - it's a national repository.
"So I think this kind of mistake is a wake-up call."
Gottfried Lindauer (1839-1926) was New Zealand's best-known painter of Maori subjects in the late 19th and early 20th centuries. He was known for the accuracy of his portraits, which is why they are sought-after historical records.
The library put the portrait in its catalogue and also provided an image of it to the New Zealand Listener in 2014 for a major article on New Zealand portraiture.
However, earlier this year Auckland Art gallery conservator Sarah Hillary analysed the painting as part of her preparation for a book on Lindauer.
Her forensic study indicated that there was no way the work could be a Lindauer as it contained titanium dioxide, which was not available as an artist's pigment when Lindauer was painting. She also pointed out that the brushwork was quite rough compared with the careful brushwork of Lindauer.
The chief librarian for the Alexander Turnbull Library, Chris Szekely, told Nine to Noon the revelation was particularly disappointing for the library, and the police had been informed.
"We backed our own judgement in the face of an assessment from an external expert. Art historian Roger Blackley had commented to us on the painting's strange appearance," she said.
"We listened to his views but proceeded with the auction. Differing opinions are not uncommon in these matters, and in this instance we went with the library's in-house expertise. It is now evident that we were wrong."