Almas Guliyeva was stopped at Baku airport

Fair Trials Abroad said it expected charges against Almas Guliyeva to be dropped, or for her to be returned to the UK to receive medical treatment.

The 46-year-old, from Golders Green, north London, became ill while in custody and was taken to hospital.

Her uncle is chairman of the opposition Democratic Party of Azerbaijan.

Mrs Guliyeva was detained at Baku airport on 3 June as she was about to board a flight to the UK, having attended a funeral.

The authorities in Azerbaijan said customs officers had discovered a pistol in her luggage.

Azerbaijani newspaper Muxalifat reported Mrs Guliyeva's lawyer as saying she had nothing to do with the gun.

Her son Ilkin Gouliev, 19, claims the weapon had been planted for political reasons.

She needs to be back quickly where she belongs, with her family in London Liberal Democrat MEP Baroness Ludford

Mrs Guliyeva is married to Ilgar Guliyev, nephew of the US-based chairman of the opposition Democratic Party of Azerbaijan, Rasul Guliyev.

Ilkin Gouliev also said his mother had suffered a stroke following her arrest.

On Tuesday, lawyers from Fair Trials Abroad and Liberal Democrat MEP Baroness Sarah Ludford met Azerbaijan's ambassador to the UK, Rafael Ibrahimov.

Fair Trials Abroad and Baroness Ludford later said they were "cautiously optimistic" Mrs Guliyeva would soon be allowed home.

A joint statement said that "due to her fragile health, and under directions of doctors, Mrs Guliyeva has not yet been allowed to be questioned", but that it was due to take place on Friday.

"We expect that once Mrs Guliyeva has been able to give her side of the story the charges against her will be dropped, or at least, in view of her serious condition, the state authorities will return her to the UK so she may get the medical treatment she urgently needs."

Baroness Ludford added: "She needs to be back quickly where she belongs, with her family in London.