Sue Tilley posed for Freud over a four-year period in the early 1990s
Chelsea Football Club owner Roman Abramovich bought two paintings that were sold at record-breaking auctions last week, according to reports.
Lucian Freud's Benefits Supervisor Sleeping sold for £17.2m on Tuesday, followed by Francis Bacon's Triptych, which fetched £43m just 24 hours later.
The Art Newspaper quoted sources saying the London-based Russian billionaire was the buyer of both paintings.
A spokesman for Mr Abramovich declined to comment.
He said: "We don't get into personal matters."
The record-breaking auction in New York
The life-sized Freud painting of a sleeping, naked woman, titled Benefits Supervisor Sleeping, sold for $33.6m (£17.2m) at Christie's in New York.
ART V FOOTBALL - HOW PLAYERS COMPARE
Andriy Shevchenko - £30m
Didier Drogba (pictured) - £24m
Shaun Wright-Phillips - £21m
Jose Bosingwa - £16.2m
Nicolas Anelka - £15m
All values are estimates
Christie's described the work, which shows Jobcentre supervisor Sue Tilley asleep on a sofa, as a "bold and imposing example of the stark power of Freud's realism".
It set a new world record price for a work by a living artist.
The following day, Sotheby's sold Bacon's Triptych (1976) for $86.3m (£43m) - the most ever spent on a work by the Irish-born artist - also in New York.
The three panelled picture depicts a headless human form surrounded by three vultures and flanked by two portraits of disfigured human faces.
Meanwhile, two more paintings by Freud and Bacon are expected to fetch more than £25m when they come up for auction next month.
Freud's Naked Portrait with Reflection (1980) shows a nude model spread out on a tattered sofa and is estimated to fetch up to £15m at Christie's.
Bacon's Three Studies for a Self Portrait is expected to fetch more than £10m at the same Christie's Post War and Contemporary Art Evening Sale on 30 June.