It is alleged the pair were abducted by their mother Trudy Crofts in August and left with her husband's Moroccan family in the town of Khenifra.

As revealed by The Gazette yesterday, a deal had been struck which would have seen the youngsters, aged 12 and 11, flown back to the UK and returned to their grandmother and legal guardian Rita Astbury.

But police and solicitors for Ms Astbury say the deal has now collapsed and the Moroccan family are, for a third time, refusing to release the girls.

Ms Astbury's solicitor, Emma Schofield, said: "I've had it confirmed by the police the family in Morocco are now refusing to hand over the children.

"This is the third time that has happened. It's frustrating for everyone concerned but especially for Rita."

Ms Astbury has been the girls legal guardian since 2002 and has made a number of tearful appeals for them to be returned safely.

Det Insp Frank Walmsley, from Blackpool CID, added: "It appears the Moroccan family are unreliable. We will now go back to plan A which was to submit a letter of request to the Moroccan authorities."

The letter will ask for permission for Blackpool Police to fly to Morocco to work with their Moroccan counterparts and ask the courts to intervene.

Det Insp Walmsley added Ms Astbury may still face a long wait for the girls to return home.

Devastated at the bad news, Ms Astbury, 54, from Milbourne Street, said: "I can't believe it. I thought they were going to be coming home. This is heartbreaking."

The news comes as pictures of Carene and Shelby were released to The Gazette. They were supplied by Halim Bouhafsi, a friend of Ms Crofts' husband Abdullah "Sammy" Zroiai.

He said Mr Zroiai had sent him the pictures to show people, including Ms Astbury, that the girls were being well looked after.

The images show Carene and Shelby playing with family pets including puppies and goats and sitting in a bedroom.

Mr Bouhafsi said he was acting as a "middle man" and passing messages from Mr Zroiai, who is in Spain and trying to help get the girls back to the UK.

Yesterday he told The Gazette Mr Zroiai had allowed the girls to stay with his family in Morocco out of "loyalty and respect," to their mother.

Carene and Shelby were allegedly abducted from their home by Ms Crofts in August after she lost a third court battle to win back custody of the girls. Ms Crofts, 30, was arrested at Alicante airport. She was this week jailed for contempt of court after failing to sign a letter instructing the Moroccan family to return the girls home.

She also faces two criminal charges of child abduction and is awaiting trial.