It may be, in the words of one British diplomat, a "crap acronym", but the UK is now a founding member of the "Chuks" – joining the Czechs, Hungarians and Swedes in refusing to join from the outset the 23 other EU states preparing to endorse a new treaty to save the euro.

Unlike the Brics, this may turn out to be a short-lived grouping, as the prime ministers of the Czech Republic, Hungary and Sweden said after its birth they would consult their national parliaments on joining. Diplomats said it was unlikely the Czechs and Swedes would join, and question marks remain over the Hungarians. For the time being, at least, the EU is not divided 26-1.

Sweden, independent and neutral, is obligated to join the euro in due course but is in no rush to do so and Fredrik Reinfeldt, its centre-right prime minister, said on Friday that it preferred to operate at an EU-27 level. "We want to keep the European project together," he said.

The Swedes have misgivings about the complex legal issues clouding the proposed treaty. These concern primarily the role of EU institutions such as the commission and court of justice within the new fiscal compact.Reinfeldt, who heads a minority government, said he would consult his parliament's EU committee and the opposition, but made it plain it would be strange for non-euro Sweden to "tie itself to rules tailored for the eurozone". He added: "A non-euro country cannot reasonably sign up for that."

The Czechs are profoundly Eurosceptic and an observer said the domestic problems of Petr Necas's government were so acute that "it is unrealistic now to be part of some agreements of this kind". He added: "There are no real euro fans in the Czech Republic."Jan Zahradil, a fellow member of the Civic Democratic party and chairman of the European Conservatives and Reformists group, explicitly praised David Cameron and Necas for "defending the interests of their citizens" and refusing to surrender fiscal sovereignty."The leaders of the eurozone unfortunately missed the opportunity to transform the EU into a flexible, open structure, insisting instead on a narrow-minded and obsolete federalist concept, which leads the EU only in one direction: that of ever-closer integration," he added – welcoming a two-speed, two-tier Europe and insisting on protection for the single market.

Hungary's position remained "completely misunderstood", according to its EU affairs minister, Eniko Gyori, who said the country was not boycotting the new pact. "We are in favour of stronger rules so that the troubles on the markets cease, as they also affect our economy," she said, indicating that the parliament in Budapest could wait until March before deciding on action.Hungary has recently admitted it will have to seek IMF/EU funding to help its stricken economy – which has junk status for its sovereign debt – so is heavily dependent on approval from Brussels.

But Viktor Orban, its premier, has put his Fidesz party at the head of an ultra-nationalist campaign to rewrite not only Hungary's constitution but its history. He made it plain he had no authority to give up national sovereignty, and said: "The deal means stricter rules … those who join would lose veto rights and so on."

The comments suggest that Cameron may yet avoid complete isolation under the new euro settlement.

The Irish government said on Friday it was getting legal advice on whether Ireland needed a referendum on a new European treaty.

Taoiseach Enda Kenny said its attorney-general, Marie Whelan, will have to forensically examine any fiscal union deal struck at a European summit.

"The first thing is that once the text has been approved and agreed, every country has to do its own thing," said Kenny in Brussels. "In our case, the attorney-general will have to analyse that, forensically examine it and give official and formal information and advice to the government as to whether a referendum is required or not."