Matisse masterpiece held in the National Gallery is at the centre of a £24.6 million legal battle after the family of the woman in the painting claim it was stolen by the Nazis

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• London gallery accused of owning Matisse work which was Nazi looted art 
• The National Gallery said it would defend itself against the accusations
• Family of the subject in Portrait of Greta Moll have launched legal action
• Gallery said the claim is undermined because she moved to Wales in 1947 

A Matisse masterpiece which is at the heart of a row over ownership is not Nazi looted art, the National Gallery has insisted.

The gallery said it will 'robustly defend' itself against accusations that a portrait by Matisse in its collection had been stolen from the original owners.

It comes after three grandchildren of the subject in the 1908 Portrait of Greta Moll launched legal action seeking £24.6million, alleging the painting was taken from them following the Second World War.

Portrait of Greta Moll by Henri Matisse, which is at the heart of a row over ownership

But the claim that the Moll family lost the celebrated artwork in the fallout from the Third Reich is undermined by the fact Greta Moll moved to Wales in 1947, the gallery said.

At this time, it is claimed, the family were still in possession of the painting.

The National Gallery said in a statement: 'We understand that both Greta Moll and her husband were living in Germany during the Second World War.

'Some years after the war ended, and following the death of her husband in August 1947 (when the family say the painting was still in their possession), Greta Moll moved to Wales. This case therefore does not concern Nazi looted art.'

It said the purchase of the portrait in the UK in 1979 was therefore 'in good faith', adding that the family's decision to lodge legal action in the US was without 'justification'.

Margarete Moll, known as Greta and a pupil of Matisse, lived in Germany during the Second World War, and soon afterward entrusted the painting for safekeeping from looters to an art student of her husband Oskar in Switzerland, according to the complaints.

But the student absconded with the painting, which later passed through Manhattan's Knoedler & Co art gallery and other hands until it was bought in 1979 by the National Gallery, which ignored a 'red flag' that the work might have been stolen, it is claimed. 

According to court papers, the museum's newly-installed director Dr Gabriele Finaldi refused to return the oil-on-canvas work in September last year, citing 'statutory constraints.'

But Moll's grandchildren said that by keeping ownership of the painting, while allowing its exhibition and selling merchandise depicting it in New York, the National Gallery 'has ignored the international legal standard that such war-related lost property should be returned to its true owners.'