Italy has grounded two planes used by NGOs to search for migrant boats in distress in the Mediterranean.

The planes – Moonbird and Colibri – are operated by the German NGO Sea-Watch and the French NGO Pilotes Volontaires respectively and have been flying reconnaissance missions over the Mediterranean since 2017.

For the past month neither has been able to take to the skies after the Italian civil aviation authority said they could “only be used for recreational and non-professional activities”.

Last year, Malta blocked Moonbird from operating out of the country and the aircraft stood still for over three months. Since 2017, the NGOs have been the subject of numerous investigations in Italy and Malta that critics say have slowed down rescue operations.

Thousands of people have died in the Mediterranean from among hundreds of thousands attempting the crossing from North Africa to Europe in recent years, although the number making the voyage has been declining.

On Tuesday the United Nations refugee agency said about 40 people were feared dead or missing after the latest wreck of a boat off the coast of Libya, while about 60 people may have been rescued. Unseaworthy vessels overloaded with migrants trying to reach Europe regularly capsize off Libya. Last week more than 100 people died, and a boat with about 250 capsized last month.

Since coming to power in June 2018, Italy’s far-right interior minister, Matteo Salvini, has repeatedly taken a hard line against migrants and the NGOs attempting to rescue them at sea. On Monday, the head of Médecins Sans Frontières (MSF) in Spain launched a scathing attack on western governments that hinder the work of humanitarian organisations, warning that “the criminalisation of solidarity” and the “politicisation of humanitarian action” are becoming increasingly normal.

In an interview with the Spanish news agency Efe, David Noguera referred specifically to the rhetoric of Salvini.

Noguera said that while many governments in conflict areas “have no qualms about depicting NGOs as being complicit actors … we’re now seeing that in Europe with the discourse of people like Salvini, who directly accuse NGOs of being mafias and of charging to rescue migrants”.

He added that the normalisation of “once-inconceivable” attitudes and situations should be deeply troubling for society. “If someone had told us five years ago that 20,000 people would die in the Mediterranean, or that children crossing the border would be separated from their parents in the US, we’d never have believed it,” said Noguera.

“But now it’s become normalised to an astonishing extent, with hardly any resistance, as if it was something usual.”

He called on society to do more to build a consensus so that migrants are helped and integrated. “It’s unbelievable when you see comments on Twitter or on online newspapers about letting people die in the sea, or sending them back to Libya – which everyone knows is a pit of suffering.”

Noguera also spoke out about the increased targeting of NGOs and hospitals in conflicts such as Syria.

“If we’re made out to be part of the conflict, the consequence is that there are people who feel they can attack us legitimately and that means we have to pull out of the zone,” he said.