A Dunkirk-style sea rescue of the thousands of Britons stranded abroad by the volcano ash flight ban was being planned by the Government last night.

Royal Navy ships may be joined by commandeered civilian vessels to bring home British citizens, who have now been stuck since last Thursday across Europe and around the world.

It is possible that Spain, which is largely unaffected by the giant ash cloud from the Icelandic volcano, allowing aircraft to fly in its air space, may be used as the "hub" of the operation for people who are stranded outside Europe, principally in Africa and North America.

Last night, Gordon Brown was speaking to Jose Luis Zapatero, the Prime Minister of Spain and also the current president of the EU, to discuss the idea.

The giant rescue plan, which has shades of the evacuation of the British Army from the Belgian Channel port of Dunkirk in May 1940, was drawn up last night at a meeting of senior ministers in Downing Street presided over by Mr Brown. It was also attended by senior staff from the Met Office and the Government's chief scientific adviser, Professor John Beddington. The plan was unveiled at an impromptu press conference outside No 10 afterwards, by the Business Secretary Lord Mandelson,the Foreign Secretary David Miliband, the Transport Secretary Lord Adonis, the Security minister Admiral Lord West and the Cabinet Office minister Tessa Jowell. "We need to look at every single logistical operation for getting our people home, and that's what we're going to do," Lord Mandelson said.

It was noticeable that Lord Mandelson took on the task of public reassurance, and that Mr Brown himself did not appear – presumably to avoid charges of making political capital out of the situation, in the run-up to the general election. But the Prime Minister is central to the rescue operation and will preside over a meeting of the "Cobra" civil contingencies committee this morning.

The Government is acting because there is increasing concern that the ash cloud from the volcano Eyjafjallajoekull, which has now drifted over much of Britain and northern Europe and has made flights for aircraft with jet engines hazardous, shows no sign of dispersing.

The volcano is continuing to erupt – although it appeared to have slackened slightly yesterday – and north-westerly winds are bringing the ash directly to Britain from Iceland. The current weather pattern shows no sign of shifting before mid-week at the earliest. Last night, the Met Office said it would still not be safe to fly commercial aircraft across most of Europe today. Restrictions on flights across UK airspace will remain in place until at least 7pm today, the air traffic control company Nats said last night.

European transport ministers are meeting by video conference later to discuss the situation. However, there are some suggestions that the restrictions are too stringent and there is a growing call for them to be lifted. The transport ministers will be considering new data on volcanic ash and aircraft engines gathered over the weekend during test flights run by a number of airlines, including KLM, Lufthansa, Air France and last night, British Airways.

They will look at whether, in the light of the new data, the safety rules which have prevented airlines from operating can be adjusted. But Lord Adonis said last night that the rules were international and were being applied in exactly the same way in every country across Europe. Lord Mandelson added: "The Government's primary concern and commitment is for the safety of air passengers. You cannot simply take risks or vary rules except on the basis of independent, objective scientific advice."

In the meantime, thousands of people are facing increasingly stressful circumstances in foreign airports as far away as Beijing. Mr Miliband said the Foreign Office's consular officials around the world were making themselves known to stranded passengers at airports and other places, to provide information and help with visa, health and other issues. All passengers who are stranded and who have an EU carrier have a right to food and accommodation, Lord Adonis said, advising those who had not yet benefited to contact their airline. The Government was doing all it could to maximise new land transport capacity, he said, with additional trains running between London and Scotland, and on the Eurostar line to Paris and Brussels, with a big increase in the number of coaches running through the Channel Tunnel.

Airlines and the travel industry are believed to have already run up losses of more than £1bn since Europe became a no-fly zone. Asked if there might be an emergency bailout for affected airlines, Lord Mandelson said: "Obviously there is tremendous financial pressure on the airlines. We will continue to talk to them and examine possibilities, but I have to stress there are European rules that operate here."