More than 200,000 rental sector tenants across England are estimated to have faced a "revenge eviction" in the last year after asking for a problem with their home to be put right, according to research for charity Shelter.
One in 50 (2%) private sector tenants said they had been evicted or served with an eviction notice because they had complained to their landlord, letting agent or council about something that was not the tenant's responsibility, such as a repair that needed fixing.
This equates to more than 213,000 people if the figures are projected across England.
The YouGov survey of more than 4,500 private renters suggested that many more renters are too scared of losing their home to complain at all.
One in 12 renters (8%) say they have avoided asking their landlord to repair a problem or improve conditions in the last year because they were scared of eviction.
More than two-fifths (41%) of renters said they have experienced mould in their homes in the past year, while a quarter (25%) have lived with a leaking roof or windows, and 16% have had electrical hazards.
The charity said that a family in Norfolk had been handed an eviction notice three weeks after reporting damp and mould to their landlord, while a couple in Brighton who complained about a broken thermostat, mould and damp that was affecting their health, were served an eviction notice a week later.
A family from Lancashire was evicted after complaining about a leaking roof, who were told by their landlord that it "wasn't worth his while" to fix the problem, Shelter said.
The charity is launching an online petition at www.shelter.org.uk/9millionrenters, campaigning for the Government to protect renters from "unfair" evictions.
Campbell Robb, chief executive of Shelter, said: "No-one should lose their home for asking their landlord to fix a problem, yet these shocking findings uncover the true scale of unfair evictions taking place across the country."
Research was commissioned by Shelter and British Gas as part of their partnership to improve the conditions of privately rented homes.
Matt Hutchinson, director of flat and house-share website SpareRoom.co.uk, said the strength of demand for rental properties in some areas of the UK means that the website is seeing as many as 12 people compete for every room advertised.
He said: "With demand far outstripping supply in the private rented sector, tenants can be left feeling utterly powerless to complain about living standards - because they know they're easily replaced.
"Everybody has the right to expect a decent standard of accommodation, whether they own, rent or share their homes. It's unacceptable to have people living in poor conditions simply because they're afraid to complain for fear of eviction."
Mr Hutchinson cautioned that regulatory intervention should not make it harder for good landlords to operate.
Housing Minister Kris Hopkins said: "Today's YouGov poll clearly shows that 'revenge evictions' are rare, while the recent English Housing Survey showed the vast majority of tenants satisfied with the service their landlords provide.
"But all tenants have a right to expect a decent service for the rents they pay and it is clearly unacceptable that anyone should hold back from requesting repairs, out of fear of being evicted.
"We're determined to root out the rogue landlords who are behind this behaviour, and have provided guidance and over £6.5 million to councils to tackle them.
"But I want to see what else we can do to ensure anyone renting privately can do so confident they will get a good deal, while at the same time ensuring good landlords are free from the burden of red tape and bureaucracy."