"The reality is that today I am the focus of criticism, noise, hatred and tension," Carlos Mazon said in a televised address.

"I can't go on any more."

Mazon will remain as a lawmaker in the Valencia regional parliament and is expected to be replaced as the region's leader by another member of his conservative Popular Party (PP).

He has faced fierce scrutiny over his handling of the October 29, 2024, catastrophe that killed more than 230 people, swept away 130,000 vehicles and damaged thousands of homes.

But has consistently rebuffed calls for his resignation.

Last week, relatives of the victims shouted "murderer", "coward" and "get out" at Mazon when he arrived for a state memorial service for the victims in the regional capital, also called Valencia.

Mazon's regional administration -- primarily responsible for the emergency response under Spain's decentralised system -- sent an alert to residents' mobile phones when flooding had already started in some places.

The alert, which told residents to shelter in place, came more than 12 hours after the national weather agency had issued its highest alert level for torrential rains.

Critics allege the regional delay in raising the alarm cost lives.

Despite signs of severe flooding, Mazon did not change his schedule.

He went ahead with a lengthy lunch with a journalist and appeared in photos tweeted by his staff attending an event on Valencia's sustainable tourism strategy.

- 'Made mistakes' -

Mazon said on Monday he "should have had the political vision" to cancel his appointments and visit the affected areas on the day of the disaster.

"I know I made mistakes. I acknowledge them and I will live with them all my life," he added.

"I have asked for forgiveness and today I repeat it. But none of them were due to political calculation or bad faith."

Mazon, whose conservative PP sits in opposition to the Socialist-led national government, has argued his administration did not have the information needed to be able to warn people sooner.

"We did our best under unimaginable circumstances, yet in many cases it was not enough," he said last week before the state memorial.

Campaigners have staged regular protests against Mazon, often on or near the monthly anniversaries of the disaster.

More than 50,000 people, many carrying photos of family members who died in the floods, took to the streets of Valencia city in the latest such demonstration on October 25 to demand Mazon's resignation.

- Majority back resignation -

Residents told Spanish media that by the time they received the mobile alert, muddy flood water was already surrounding their cars, submerging streets and pouring into their homes.

One resident of the town of Paiporta, one of the worst affected, told local television the alert came when he was stranded in a tree with bodies floating past.

In an opinion poll published last month in El Pais newspaper, 71 percent of Valencia residents said Mazon should resign.

Analysts said Mazon had become a burden for the PP national leader, Alberto Nunez Feijoo, who had continued to back his regional ally.

Rosa Alvarez, who heads an association representing flood victims, credited pressure from the protests for Mazon's resignation.

"His party didn't make him resign.

"It was the families of the victims and all the people who have supported us, who have given us encouragement and affection, who made him resign," she told news radio SER.

Alvarez's 80-year-old father died after the walls of his home in Catarroja were knocked down by the raging torrent.

Last year's floods hit 78 municipalities, mostly in the southern outskirts of Valencia city on the Mediterranean coast and generated 800,000 tonnes of debris.