The unusual cause was only discovered after a two-hour search of the bedroom by firefighters and the news stunned homeowner Sharon Beddis, 43.

The mum-of-two had fled her house, on Lynwood Crescent, with her friend after they noticed smoke pouring down the stairs at about 1.40pm on Saturday.

She said: "I just heard some clattering upstairs, and thought one of my sons had come home. We didn't smell anything at all. There was nothing to warn us. But we saw the smoke and my friend said there's a fire upstairs.

"So we ran outside and called the fire brigade.

"I couldn't believe it when they told me the mirror had caused it. They had been asking me if there was anything in that corner of the room which could have started a fire, but there were no plug sockets there. Then they said it must have been the mirror. I just couldn't believe a mirror could have cause so much devastation."

Pontefract watch manager John Lloyd said: "Sunlight has shone onto a dressing table mirror and the effect caused the curtains to set alight and the fire spread to the rest of the room.

"It is unusual for this to happen but not unknown.

"The weather doesn't have to be hot, the thing is the angle of the sun. It probably only happens at this time of year because the sun is so low in the sky."

Sharon and her partner were due to fly to The Gambia on holiday this week but she has lost all her clothes and her passport in the fire.

She also warned other people to be careful if they have a mirror on their windowsill which she said was "timebomb" waiting to start a fire.

Sharon, who is now living in rented accommodation while her house is cleaned, said: "It was one of those revolving mirrors which has one normal mirror and a magnifying one. The sunlight had caught the magnifying side. Those mirrors are on sale everywhere and so many people have them.

"I'd had this one for two years. It's been like a timebomb.

"If it had happened while we were on holiday, of if I'd been out, I'd have lost the house."

Watch manager Lloyd added that smoke alarms were not fitted at the property. For a free home safety check call 0800 5874535.