Less than a month before leaving office, the prime minister Theresa May has urged mandatory new design standards to “ensure high-quality homes, more social housing, and further tenant rights as part of an ongoing housing revolution.”

Addressing the Chartered Institute of Housing conference, the prime minister admitted that “not enough homes had been built for many decades,” and stressed that the “quality of housing must not be compromised by the drive to build more homes.”

Setting out next steps on the social housing green paper agenda, with an action plan expected in September, the prime minister’s intervention comes as government figures indicate that, by autumn, a million homes will have been added in under five years.

The prime minister said: “This is a government with a bold vision for housing and a willingness to act on it. A government that has delivered radical reforms for today, and the permanent structural changes that will continue to benefit the country for decades to come. The housing shortage in this country began not because of a blip lasting one year or one Parliament, but because not enough homes were built over many decades. The very worst thing we could do would be to make the same mistake again.”

The government says that last year more additional homes were delivered than in all but one of the previous 31 years. But, calling for new regulations to mandate developers to build higher-quality housing, the prime minister made it clear that the quality of housing must not be compromised by the drive to build more homes.

The prime minister said: “I cannot defend a system in which owners and tenants are forced to accept tiny homes with inadequate storage… where developers feel the need to fill show homes with deceptively small furniture… and where the lack of universal standards encourages a race to the bottom.”

However, Labour’s shadow housing secretary John Healey dismissed the prime minister’s comments as “a lame duck announcement from a lame duck PM.”

Healey said: “This is a lame duck announcement from a lame duck prime minister. Her ministers have launched 83 housing consultations in the last three years, but little action or legislation has followed. Today she still only promises change on building standards and social housing in the future. Deep cuts to government investment mean the country is now building 30,000 fewer social rented homes each year than when Labour was in government. After nine years of failure on housing, it’s clear the Conservatives have no plan to fix the housing crisis. They should back Labour’s long-term plan for a million new genuinely affordable homes, with the biggest council house building programme for nearly 40 years.”