French President Francois Hollande and his companion Valerie Trierweiler (L) attend the inauguration of the Auzelou community hall in Tulle, central France in this file photo. REUTERS/Pierre Andrieu/Pool/Files

Paris - French First Lady Valerie Trierweiler was set to spend a fourth night in hospital Monday after doctors decided she needed “more rest” following revelations of an alleged affair between President Francois Hollande and an actress.

Trierweiler, 48, was admitted to a Paris hospital on Friday, hours after the alleged liaison between Hollande and actress Julie Gayet was revealed by gossip magazine Closer.

The twice-divorced mother of three was said to require “rest” after suffering the blow of the media report. She was initially expected to be discharged on Monday, but one of her aides told France Info radio that doctors had prescribed a longer stay. “The doctors consider that she needs more rest so she will remain in hospital ... She needs to recover after the shock she suffered. She needs tranquility,” the unnamed aide was quoted as saying. The scandal threatens to overshadow Hollande's biannual press conference - scheduled for Tuesday - at which he plans to set out his policy priorities for the coming year.

The 59-year-old Socialist leader, who declared Trierweiler to be the “woman of (his) life” in 2010 - a few years after leaving the mother of his four children, politician Segolene Royal, to be with her -has accused Closer of invasion of privacy.

He has denied having an affair with Gayet, who is 18 years his junior.

A survey in weekly newspaper Le Journal du Dimanche on Sunday showed 77 per cent of the French supporting Hollande's view that the affair is a private matter.

The French media are however demanding answers Tuesday about Trierweiler's status as the first lady.

Trierweiler lives in a wing of the Elysee Palace, where she has five staff at her disposal.