Several companies came under fire after the October 29 catastrophe for ordering employees to keep working despite a red alert issued by the national weather agency.

The firms said the authorities failed to inform them sufficiently and sent telephone alerts too late during the European country's deadliest floods in decades.

The new measure aims to "regulate in accordance with the climate emergency" so that "no worker must run risks", Labour Minister Yolanda Diaz told public broadcaster RTVE.

If emergency authorities raise the alarm about a risk, "the worker must refrain from going to work", said Diaz.

Employees can resort to a reduced working day beyond the four-day period, a mechanism that already exists for emergencies, the government said.

Economy Minister Carlos Cuerpo warned the cost of extreme weather events could double by 2050 as the government confirmed 2.3 billion euros of fresh aid for flood victims.

Scientists say climate change driven by human activity is fuelling the increased length, frequency and ferocity of natural disasters.