San Francisco voters were poised on Tuesday to defeat a controversial ballot measure to curb short-term home and apartment rentals, handing a victory to companies such as Airbnb, early results showed.

With about 65,000 ballots counted, about 61 per cent of voters had moved against Proposition F, which would cut the number of nights San Francisco homes or bedrooms can be rented to 75 each year, among other limitations.

Prop. F's failure is a victory for home- and apartment-rental company Airbnb, the tech firm targeted by the measure put forward by affordable housing advocates and tenants' rights attorneys.

Airbnb spent more than $8 million to defeat the measure, canvassing neighbourhoods with volunteers and propping up billboards in a campaign orchestrated by Washington political operative Chris Lehane.

The measure would also provide neighbours greater power to sue rental property owners if they believe they are violating the law. - Reuters