The Bronte Society has cast doubt on claims a painting being auctioned in Northampton this month is a portrait of the famous literary figure Emily Bronte.

Ann Dinsdale, collections manager at the Bronte Parsonage Museum, said the society doubted the provenance of the oil painting and would not be bidding on it next Thursday.

“We are not 100 per cent convinced it is Emily. There isn’t enough provenance on the painting and there is an element of doubt about it,” she said.

“There are two portraits of Emily, both in the National Portrait Gallery, and they don’t bare a striking resemblance to this one. The experts are saying the woman in the painting is wearing the kind of clothes Emily would have worn, which probably thousands of other women of that period were wearing. They have done a huge amount of research on that painting but we are still not convinced.”

But art experts, who have assessed the picture, say there is strong evidence to suggest it could be of Emily Bronte.

The oil painting, which shows a young woman wearing a straw bonnet held in place by a silk scarf, was painted earlier than previously thought.

The picture, recently given to auctioneers J P Humbert of Northamptonshire by a retired headmaster, was found to have been painted circa 1840, making it contemporary with the age of the possible subject – Emily Bronte died in 1848.

It is almost identical to a print of a portrait of the writer published in the July 1894 issue of The Woman At Home, which itself was attributed to Charlotte Bronte. It is thought the artist responsible for the newly-found picture may be John Hunter Thompson (1808-1890) of Bradford who was a portrait artist and friend of Emily’s brother Branwell.

As well as that, written on the back is “Emily Bronte – Sister of Charlotte B... Currer Bell”, and on the backing paper “Emily Bronte/Sister of Charlotte Bronte/Ellis Bell”. Currer and Ellis Bell were the pen names of Charlotte and Emily Bronte from the winter of 1845 when the sisters published their poems and adopted pen names.

Auctioneer Jonathan Humbert said the attribution confirms that the portrait is earlier than previously thought.

“After much research, we are confident this portrait, recently discovered, is of Emily Bronte,” he said.

“So many factors support this contention and, as such, this represents a very important study of one of English literature’s most perennial figures.”

The oil on panel painting is set to go on sale at JP Humbert Auctioneers in Towcester, Northants, at a provisional estimate of £10,000 to £15,000.

The sale coincides with an auction where the society will be bidding for a rare Charlotte Bronte manuscript the Young Men’s Magazine.