Labour have attacked Southampton Conservatives for “misleading” voters over their support for new laws to control student houses.

It has emerged that Tory leader David Cameron signed a motion calling for new planning definitions for houses in multiple occupation (HMOs) to be revoked in one of his final acts in parliament.

Labour said the move would have killed off a new requirement for landlords to get planning permission if they want to turn family homes into houses for three or more sharers.

Campaigners in Southampton have long been calling for a clampdown on the spread of HMOs, largely occupied by students, which they say have blighted areas such as the Polygon and Highfield with parking problems, overflowing rubbish bins and noise nuisances. Labour candidate for Southampton Test Alan Whitehead, who as a city MP has lobbied for new HMO laws, said his Tory rival Jeremy Moulton had been humiliated by Mr Cameron’s actions.

Mr Whitehead said: “He should apologise for misleading voters – he first opposed the new measures and then cynically claimed he supported them all while his own party leader was planning to speak out against them. He must have known of this, and he should apologise immediately.”

HMO campaigner Jerry Gillen, chairman of the Highfield Residents’ Association, added: “We have worked in good faith with all parties to secure these protections to family homes. For David Cameron and the National Landlords’ Federation to betray us through the use such an obscure parliamentary motion is incredibly disappointing.”

Itchen Lib Dem candidate David Goodall said: “If Mr Moulton supports it and his leader doesn’t, that’s his problem. We’re in favour of this legislation”.

But Conservative Test candidate Jeremy Moulton, who has campaigned for more powers to tackle HMOs, said the early day motion was a normal parliamentary procedure to ensure a debate of laws.

Councillor Moulton said: “It’s the job of the opposition to debate legislation. Alan Whitehead should have known that as he’s been an MP for 13 years.”

New rules this month now allow councils to introduce licensing schemes to control HMO hotspots without Government permission.