Inappropriate cavity wall insulation in homes has become “a scandal”, a Welsh MP has said.
Arfon MP Hywel Williams claimed millions of homes had the insulation installed by successive government-backed schemes which has led to damp, mould and condensation.
He called on the UK government to take responsibility for the “dreadful mess”.
The UK government said it was committed to ensuring consumers are protected.
The Welsh Government said it has been working with partners, including the UK government, to address the issues and improve the system.
The insulation is meant to make homes warmer and more energy efficient but if installed incorrectly, or in unsuitable properties, it can lead to damp.
Driving rain is also a problem, especially in Wales.
Mother-of-three Anna Phillips from Barry, Vale of Glamorgan, started having problems in her three bedroom home seven years ago after buying the property in 2004.
Cavity wall insulation had been installed by the previous owners.
Ms Phillips said damp started coming through in 2010 and the insulation was removed early last year after she contacted the industry-funded guarantee organisation Cavity Insulation Guarantee Agency (CIGA).
“It was soaking wet, absolutely drenched. It took them two days to take it all out due to how poor it was,” she said.
The mental health support worker said heating bills were higher as the mould and damp had affected the whole house and she believed it had impacted on her family’s health.
Speaking about her three children – aged 11, nine and four – she added: “They’re poorly all the time, two suffer with eczema, their chests, they’re continuously coughing, it’s freezing.
“You can have the heating on all day in this house and you don’t feel it, you really don’t”.
Last year, a report by the construction research organisation BRE concluded there should be a nationwide survey of the problem in Wales.
According to the investigation, about 900,000 homes have been built with cavity walls.
Mr Williams will be debating the issue in Westminster on Wednesday and said he was currently dealing with 60 cases in his constituency.
He has called on the UK government to find out exactly how many people have been affected, rectify failed installations and provide proper compensation.
“The scheme was pushed as a free scheme with the backing of the government which would save people £250 per year or so in their heating costs and clearly older, people with disabilities and poor people actually took advantage of it because of the obvious hard sell,” he said.
A spokesman from the UK government’s Department for Business, Energy and Industrial Strategy said: “The government is committed to ensuring that consumers are protected when choosing cavity wall insulation.
“That’s why installations carried out under the Energy Company Obligation (ECO) are subject to a number of strict quality standards and Ofgem requires cavity wall insulation to come with a minimum 25 year guarantee.”
A Welsh Government spokesman said it was “in discussion with the main scheme operator, CIGA, about our concerns around the adequacy and reliability of pre-installation property assessments, the need for accessible information to householders about installations and future maintenance and customer focussed claim and complaint resolution procedures”.
“We are currently reviewing the conditions of authorisation for scheme operators dealing with cavity wall insulation in relation to these areas of concern,” the spokesman added.