Anger and grief are still raw four months after the European country's worst natural disaster in decades killed 232 people, including 224 in the eastern Valencia region.

In a demonstration called by dozens of unions and civil society associations, protesters holding pictures of their dead loved ones chanted "Mazon resign" and marched behind a banner reading "our relatives died due to your incompetence".

Signs emblazoned with slogans including "Mazon in prison", "murderers" and "we don't forgive, we don't forget" featured alongside a giant cardboard cutout representing Mazon with blood-stained hands.

The central government's office in Valencia put the number of demonstrators at around 30,000.

Spain's regions are responsible for emergency management in the decentralised country, meaning Mazon fronted a response widely judged to have been inadequate.

A mass alert reached residents' telephones only after muddy floodwater was already ravaging the region, while many stranded residents were left without food, water or power for days.

- 'He's a liar' -

Mazon attracted fresh fury this week after offering a different account of his whereabouts on October 29, when torrential rain began triggering the floods that engulfed homes and tossed vehicles.

"He's a liar, and he doesn't even know how to keep up with his own lies, one after another," retiree Inma Manez, 66, told AFP at the protest.

Amparo Alamar, a 64-year-old teacher, said: "No one wanted this. But that's one thing, and another is lying... and getting caught -- they're contradicting themselves."

The ruling Socialists have urged the leader of Mazon's conservative opposition Popular Party (PP), Alberto Nunez Feijoo, to remove him from office.

Feijoo "knows Mazon is toxic" and can end the "unbearable situation" by sacking him, Socialist Science Minister Diana Morant told reporters in the flood-hit town of Picanya on Saturday.

But PP spokesman Miguel Tellado said the Socialists were "using the pain of the Valencian people to engage in the crudest, lowest form of politics. That is intolerable".

Mazon has consistently rebuffed calls to quit and vowed to lead the colossal recovery effort through to the end of his term in 2027.

Saturday's protest was the fifth in a series of anti-Mazon demonstrations that began with 130,000 people rallying in Valencia in November.