A council which is to sell an LS Lowry painting to balance its books could lose its museum accreditation, it has been warned.
A Riverbank was bought by Bury Council in Greater Manchester for £175 but could now fetch up to £500,000.
The council decided last week it was to go on sale to help plug a £10m deficit.
Now the government's Museums, Libraries and Archives Council (MLA) said it may remove the town's museum accreditation. It is due to meet council bosses.
The MLA, which represents the vast majority of public art galleries and museums in the UK, said that auctioning a painting to benefit council finances was against its guidelines.
Emmeline Leary, from the MLA, told the BBC News website that Bury Museum and Art Gallery's accreditation could be under threat.
"The planned sale is unusual," she said.
"Most councils take their role of guardian of collections very seriously and understand how important they are to visitors and residents."
The MLA's North West representatives will meet the council to discuss the planned sale.
Bury Council said it was taking the MLA's concerns "very seriously".
Council bosses have committed to making sure that the artwork's new home is another public gallery where it can stay on show and several approaches have already been made by potential buyers.
The Museums Association, a professional body representing the people and organisations which run galleries, has also written to Bury Council with its concerns over The Riverbank's sale.
It is currently on public show at Bury art gallery, but the council has said it "does not reflect the present collection which consists mainly of Victorian narrative paintings".
Chief executive Mark Sanders has said that the sale is "one of a range of tough choices we are currently facing".