Wet washing dried indoors can pose a serious health threat for people with weakened immune systems or severe asthma, doctors have warned.

Research shows clothes draped on drying frames or warm radiators can raise moisture levels in the home by up to 30 per cent, creating ideal breeding conditions for mould spores.

Experts are particularly concerned about Aspergillus fumigatus spores, which can cause lung infections.

Craig Mather, a fast food manager and father of three from Bolton, contracted TB in 1997.

The disease left his lungs weak and aggravated the problems he had been left with after childhood asthma.

Craig, 43, said: “I only started to recover when my consultant diagnosed chronic pulmonary aspergillosis and prescribed me special drugs to fight the fungal infection.

“However, I noticed coughing fits and night sweats particularly when I had wet washing drying on the warm bedroom radiator.

“He told me that it could be making my problems worse, so for the last 12 months I haven’t dried my clothes indoors and I’ve noticed a huge improvement in my health.”

David Denning and his team at the National Aspergillosis Centre in Manchester have issued the warning after treating a growing number of patients who have inhaled Aspergillus fungal spores.

Denning said: “One load of wet washing contains almost two litres of water, which is released into the room.

“Most of us are either immune to the fungus which grows in these humid conditions, or have a sufficiently healthy system to fight the infection.

“But in asthma sufferers it can produce coughing and wheeziness, and in people with weak or damaged immune systems, such as cancer patients undergoing chemotherapy, Aids patients and people who have an auto immune disease like Craig, the fungus can cause pulmonary aspergillosis – a condition which can cause irreparable, and sometime fatal, damage to the lungs and sinuses.

“My advice would be when in doubt dry wet washing outside, in a tumble dryer or in a well-ventilated indoor space away from bedrooms and living areas to be safe rather than sorry.”