BRUSSELS, Belgium: Airbnb and other short-term rental companies could face additional restrictions across Europe under new rules proposed this week by the European Commission to help authorities address housing shortages in tourism hotspots.

The proposal establishes the first common European framework for assessing housing measures and seeks to harmonize rules after cities including Paris, Barcelona and Venice introduced differing restrictions on Airbnb that subsequently triggered legal challenges.

A shortage of affordable housing linked to a surge in short-term holiday rentals has prompted protests by residents, particularly young Europeans.

Airbnb shares fell about three percent in morning trading on the day of the announcement.

"A year ago, I promised to tackle Europe's housing affordability," Commission President Ursula von der Leyen said in a statement.

"Today, we are taking one step in this direction. By providing more clarity and support to local authorities and communities, anchored in local realities," she said.

The proposal must be agreed with EU countries and the European Parliament in the coming months before it can become law.

Under the framework, authorities can identify areas experiencing a housing squeeze by assessing whether price-to-income levels are high or whether there has been an upward trend over the previous 10 years.

Any restrictions subsequently imposed on short-term rentals must be based on evidence, necessary and limited to affected areas, the Commission said. Measures cannot be retroactive.

Airbnb echoed comments from lobbying group CCIA Europe, which called for independent scrutiny of restrictions or effective redress. Airbnb said the central problem was a shortage of housing.

"That means focusing it (the regulation) where the shortage actually is: construction, renovation, and the homes standing empty across Europe today," George Mavros, Airbnb's head of government affairs for the European Union, said in a blogpost.

CCIA Europe's head of policy Alexandre Roure criticized the proposal for allowing cities to police their own compliance.

"Without independent scrutiny or effective redress, this proposal will remain a paper tiger, leaving disproportionate restrictions in place and undermining the legal certainty the Affordable Housing Act is meant to provide," he said.

Individual authorities will decide whether to take action under the proposed framework.

The Commission's proposal also recommends that authorities make land available for housing and modernize planning and construction processes.