Sotheby’s have launched legal proceedings against London art dealer Mark Weiss and business partner Fairlight Art Ventures over the sale of a fake portrait by Frans Hals. The auction house stated that it had ‘been left with no other option’ after the sellers ‘refused to make good on their contractual obligations’ and repay the sale proceeds.

‘Portrait of a Gentleman’ is one of several disputed works at the centre of an art forgery scandal, which broke in October 2016. Weiss bought the portrait from collector Giuliano Ruffini for a reported US$3 million (£2.5 million) in 2010. He subsequently sold it to a US collector for approximately US$10 million (£8.4 million) in a private sale brokered by Sotheby’s in 2011.

When the collector became suspicious following the seizure of another disputed work linked to Ruffini in March 2016 the portrait was subject to forensic analysis. Pigmentation tests conducted by forensic art analyst James Martin revealed that the portrait could not have been painted during Hals’ lifetime and Sotheby’s reimbursed the collector. The auction house is now demanding payment from Weiss.

While Sotheby’s claims the portrait is ‘undoubtedly a forgery’, Weiss argues that further testing should be carried out. He claims Sotheby’s has refused access to the work to enable Weiss’ experts to inspect it and has also suggested that a fresh group of conservators ought to examine it. Sotheby’s has stated that any additional tests will not alter its position on the painting’s authenticity.

It emerged last year that Christie’s auction house expressed doubts over the authenticity of the Hals portrait as early as 2008. The auction house withdrew from a proposed sales agreement with the Louvre Museum, which sought to acquire the painting for the French nation after Ruffini refused to guarantee the work’s attribution.

Weiss has vowed to ‘vigorously’ contest Sotheby’s claim.