A British mother has admitted killing her five-month-old son following a heated argument with her husband while holidaying in the south of France, prosecutors say.

The 42-year-old accountant from London is suspected of smothering her baby, known only as Daniel, as he slept beside her with his older brother in the village of Saint-Pee-sur-Nivelle.

Prosecutors alleged she confessed the killing to police, saying she was "exhausted" and "submerged by feelings of powerlessness," the Daily Mail reported.

They claimed she had been behaving erratically during the family's week-long holiday and had been behaving in a way that "drew attention to herself".

This included an incident on the eve of the baby's death during which she allegedly drove off with Daniel for several hours after an argument with her husband.

The next morning, on Saturday (3 September), the father was said to have been packing the family's belongings for the drive back to London when he heard his two-year-old son, Ben, shouting from a bedroom where he had been sleeping with his mother.

After seeing his wife emerge silently from the room, he found Daniel's lifeless body in the bed. Emergency services were called but the baby was declared dead at the scene.

Prosecutor Marc Mariee, who is leading the investigation, told reporters the mother, who has not been named, was suspected of smothering the baby "with her own hands".

"The mother told officers she had smothered Daniel," he was quoted as saying by the Daily Mail. "She said she was submerged by feelings of powerlessness that led her to this act. She said she was exhausted."

The woman was later seen by a psychiatrist who described her as 'very disturbed', the prosecutor added. Daniel's body has been moved to Bordeaux where an autopsy is expected to be carried out this week. Mariee said the woman had previously been treated for depression in hospital in the UK. She had no known history of violence.

The gite's owner, who lives on the ground floor, said the family had appeared 'pleasant and happy' apart from the row on the eve of Daniel's death, adding: "They seemed like a perfectly normal couple to me. On the final night there were raised voices and she drove off with the baby for several hours."