Spain has denied the US permission to use jointly operated military bases on its territory to attack Iran as Madrid stepped up its criticism of the “unjustified and dangerous military intervention”.

Spain’s socialist prime minister, Pedro Sánchez, has explicitly condemned the US and Israel’s “unilateral military action” against Iran, warning that it is contributing to “a more hostile and uncertain international order”. The rebukes have been reinforced by his government’s refusal to allow the US to use bases in Rota and Morón for the continuing strikes against Iran.

José Manuel Albares, Spain’s foreign minister, said on Monday that while the government wanted “democracy, freedom and fundamental rights for the Iranian people”, it would on no account allow its bases to be used in the ongoing military action.

“I want to be very clear and very plain,” he told Telecinco. “The bases are not being used – nor will they be used – for anything that is not in the agreement [with the US], nor for anything that isn’t covered by the UN charter.”

The defence minister, Margarita Robles, was similarly emphatic, saying neither of the bases had been used in the US military operation. “There is a deal with the US over these bases, but our understanding of the deal is that operations have to comply with international legal frameworks and that there has to be international support for them,” she told reporters.

Maps compiled by the flight-tracking website Flightradar24 showed that 15 US aircraft have left Rota and Morón since the US and Israel began their attacks over the weekend. At least seven of the planes were shown to have landed at Ramstein airbase in Germany.

US defence officials declined to comment on the reasons for the departures.

On Saturday, Sánchez said Donald Trump and Benjamin Netanyahu’s offensive was making the world less stable and called for a lasting political solution to the conflict.

He returned to the theme in a speech in Barcelona on Sunday. “Today, more than ever, it’s vital to remember that you can be against a hateful regime – as Spanish society is as a whole when it comes to the Iranian regime – and, at the same time, against an unjustified and dangerous military intervention that is outside international law,” he said.

Sánchez’s blunt condemnations are unlikely to endear him to Trump, who last year tore into Spain for refusing to accept Nato’s proposal for member states to increase their defence spending to 5% of their GDP. But the Spanish prime minister’s comments are in keeping with his status as one of Europe’s most outspoken leaders. Sánchez has been among the most vocal European critics of both Israel’s war in Gaza and the EU’s response to it.

Other European leaders have sought to hedge their bets over Trump’s latest attempt to secure regime change abroad. The UK prime minister, Keir Starmer, did not initially allow US forces to use Diego Garcia or any UK airbases because of doubts about the legality of the strikes. But he changed his position on Sunday after Iran launched a wave of retaliatory missile and drone attacks on targets across the Middle East – one of which hit a UK airbase in Cyprus.

In a joint statement with France and Germany released earlier on Sunday, the UK said: “We will take steps to defend our interests and those of our allies in the region, potentially through enabling necessary and proportionate defensive action to destroy Iran’s capability to fire missiles and drones at their source.”

Trump reacted to the change of heart by saying the UK had taken “far too long” to allow US forces to use its bases.

The German chancellor, Friedrich Merz – who is scheduled to meet Trump in Washington on Tuesday – said he appreciated the “dilemma” when it came to how to respond to Iran’s pursuit of nuclear weapons and its oppression of its own people.

He added: “So we’re not going to be lecturing our partners on their military strikes against Iran … Despite all the doubts, we share many of their aims.”

The European Commission president, Ursula von der Leyen, has called for a lasting “diplomatic” solution to the crisis in Iran, adding that the bloc would work hard to prepare “for the fallout from these recent events”.