A post-mortem examination revealed that Alice Wardle, 67, and Milly Bowman, 62, had tried to struggle from under the bed’s heavy wooden casing after it fell on top of them.

The cause of death was recorded as asphyxiation caused by the pressure of the frame bearing down on the women, whose families are planning to sue the owners of the Levante Club apartments in Benidorm.

They claim that the women, who were both grandparents and widows, would have been rescued if the maid had reported the apartment door locked from the inside for days on end.

The holiday complex has begun an investigation into how the screws holding the casing to the wall came loose. The frame came away from the wall and fell on top of the women after they had lowered the bed, tightly encasing them.

One theory is that the women, from Gateshead, failed to extend the legs at the end of the bed, which in turn put pressure on the frame, causing it to fall.

Carole Gregory, Mrs Bowman’s daughter, said that relatives were trying to come to terms with the possibility that the women were conscious for much of the time and became exhausted as they tried to push the casing off them.

Ms Gregory, 44, said: “It is such an appalling way to die. When the post-mortem results were given to us, we couldn’t bear it. They had been alive for days before they finally asphyxiated.

“It is hard to imagine how frightened and desperate they must have been. They were robust ladies, not frail and weak; they will have fought like hell to get out of there but were unable to move the frame.

“Awful things have been going through my mind. Were they frightened and talking to each other all that time? Did they scream out for help when no one was there to hear? Did they hold hands for comfort? “It is almost unbearable to think about it. We want answers.”

The women had flown to Benidorm on July 30 and were last seen in the resort the next day.

Allison Gibbons, Mrs Wardle’s daughter who was on holiday there with her family, was surprised when the couple failed to show up for a planned meeting. Over the next few days she visited the apartment block expecting to see them at the poolside.

She became increasingly anxious and on August 4 demanded that the women’s door be forced open.

Ms Gregory said: “The room was locked from the inside and the maid had visited but had not been able to get in. No one tried to find out what had happened to two elderly ladies who had suddenly vanished.

“Eventually, after Allison made a fuss, they called a technician who drilled the lock and got in.

“He couldn’t see my mum and Aunty Alice because the frame of the bed was on top of them; it completely encased them. It was when it was lifted that they found their bodies.”

It is believed that the women, who were not dressed for bed, had gone for a nap before the planned meeting when the accident happened.

Ms Gregory said: “We have taken legal advice and we believe there is a case here that must be answered. We are not looking for compensation. We just need to make sure that this never happens to anyone else again.”

Relatives of the sisters are now talking to other guests at the complex to see if the women may have been seen after Sunday. The holiday firm My Travel, which booked the room, has started its own investigation. A spokeswoman for the company said that 24 out of the 136 rooms at the Levante Club Apartments have the fold- down bed.

She said that the beds were 3½ years old and the cleaner had visited the property twice. The complex is owned by Centauro, a large car hire company.

Mrs Bowman, a retired cleaner, was widowed in February 1999 when her estranged husband Ronnie died. Mrs Wardle, a retired baker, was widowed last year when her husband, also called Ronnie, died.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Litvinenko murder suspect's peace offer
• Low rollers seize chance to scoop £5m on the nose
• I wish I were Chancellor now, says Ken Clarke