Bedrooms in HMOs will have to meet a minimum room size of at least 70 square feet for one person or 110 for two under proposals introduced by the government today.
The government plans to amend schedule 4 of the Housing Act 2004 so rooms that are too small must be disregarded.
Anyone in breach of the rules would be liable for conviction or a financial penalty of up to £30,000.
The government said its plans will “bring an end to ruthless landlords who exploit tenants and charge them extortionate rents to live in poor conditions”.
Gavin Barwell, housing and planning minister, said: “In order to build a country that truly works for everyone we must ensure that everyone has somewhere safe and secure to live.
“These measures will give councils the powers they need to tackle poor-quality rental homes in their area.
“By driving out rogue landlords that flout the rules out of business, we are raising standards and giving tenants the protection they need.”
But the news hasn’t gone down well with landlord associations.
David Cox, managing director of the Association of Residential Letting Agents, said: “We have to consider the unintended consequences of minimum room sizes.
“Some people are happy to take small rooms to keep their costs down. If these rooms are no longer available, where are people supposed to live?
“What’s more, if a small room in a property can no longer be let out, the costs of that room will be spread across the other tenants living in the property; pushing up their rents.
“A habitable room is essential but a one-size-fits-all policy doesn’t always work.”
Meanwhile the Residential Landlords Association wrote on Twitter: “Not what you want to wake up to: Crackdown on rogue landlords to include new minimum bedroom size”.
Other new measures include the requirement for landlords to provide adequate storage and a tightening of criminal record checks.
The government also wants to extend mandatory licensing to all shared homes with five or more people from two or more households, and to flats above and below shops and other business premises.
Currently licensing only kick-ins for homes with three or more floors and excludes homes attached to businesses, unless they are in a three storey buildings.
Cox added: “Landlord licensing doesn’t work. Councils already have a wide variety of powers to prosecute for poor property conditions and bad management practices; with penalties ranging from fines to seizure of property and even imprisonment.
“But councils don’t have the resources to undertake effective enforcement action. Imposing more burdens on councils will not mean improved standards and better conditions for tenants; it will merely mean more laws that are not being enforced.”
The government is inviting a response to the proposals online which must be submitted by 13 December 2016.