A pair of portraits by Swiss neoclassical painter Angelica Kauffman worth £1.5 million are at risk of leaving British shores unless a buyer can be found.
A temporary export ban has been placed on the artworks, which depict Mr and Mrs Joseph May and their children and date to 1780, to allow time for a buyer to come forward.
It is hoped a UK gallery or institution will acquire the pieces.
The two paintings portray a family separated by gender, making them unique in Kauffman’s work, where families are normally depicted together.
Her known collection of some 800 pieces shows no other evidence of this format.
Arts minister Lord Parkinson of Whitley Bay said: “Angelica Kauffman was one of just two female founding members of the Royal Academy.
“These fascinating portraits are highly unusual for the period, depicting an 18th-century family separated by gender.
“I hope that a buyer comes forward so that they can remain in the UK, and so that we can continue to learn more about these exceptional works of art.”
The Reviewing Committee on the Export of Works of Art and Objects of Cultural Interest, which recommended the decision, noted the female group and its allusion to the Virgin Mary was “especially beautiful”.
Committee member Professor Mark Hallett said: “Angelica Kauffman was one of the most important painters working in late 18th-century Britain and this is an especially interesting example of her output.
“Though the artist is justly celebrated for her subject pictures, Kauffman’s portraits are equivalently complex and ambitious in character.
“This double portrait of the May family, in which Mary May is pictured with her daughters, and Joseph May with his sons, is extremely unusual in splitting up its male and female subjects in such a direct way.
“At the same time, Kauffman’s adept handling of composition ensures that the two pictures elegantly complement each other.
“As well as having a powerful aesthetic appeal, the paintings offer a sensitive pictorial meditation on parental and sibling relationships, and on the different stages of childhood.
“For all these reasons, they make a powerful contribution to our understanding of Georgian portraiture.”
The decision on the export licence application will be deferred until July 24.