A union called for a tough crackdown on underused holiday homes today and even urged cash-strapped councils to compulsorily purchase them if they have an acute shortage of properties.
The GMB said its detailed research showed over 170,000 people owned a second "holiday" home in Britain, with the highest numbers in south-west England and Wales - and nearly 4,700 in London alone.
Since a house used for only a few weeks a year is very different from one occupied most of the time, the union said councils should use new powers to levy taxes on them or even buy them.
GMB said the numbers of residents with holiday homes totalled 165,095 in England and Wales and 8,181 in Scotland and Northern Ireland.
In the south-west alone over 40,000 people have a holiday home, with almost 32,000 living outside the region, the union found.
In Wales there are nearly 28,600 second homes with more than 22,300 owned by residents outside the region.
GMB general secretary Paul Kenny said: "In many areas urgent action is needed to ascertain if properties used as holiday homes are actually in use at all.
"A holiday home that is only used for a few weeks a year is very different to a holiday home that is occupied for most of the year in terms of its economic benefits to any locality.
He added: "In areas with acute housing need questions should be raised in the council chamber as to whether under-used houses should be subject to compulsory purchase."
A spokesman for the Communities and Local Government Department said: "New legislation has given councils the flexibility to remove council tax relief on second homes and empty homes and use the money to keep overall council tax bills down.
"By treating everyone equally and fairly and removing the special tax breaks for empty homes and second homes, councils have the potential to cut £20 a year off families' council tax bills."
The Local Government Association said it was not an issue it could take a national view on - "it's up to individual local authorities to decide if this is something they'd want to pursue."
If you appreciated this article then please consider donating to the Morning Star's Fighting Fund to ensure we can keep developing your paper.
Fire Minister Brandon Lewis probably had a fair idea what Sir Ken Knight would deliver when he asked him to conduct an "independent" report into fire and rescue services in England.
As LGBT activists worldwide celebrate anti-homophobia day we are reminded of prevailing prejudice
Bradford has seen the launch of a new campaign to battle the sources of child sex exploitation - and combat far-right bids to make it a racial issue