Tánaiste and Minister for Foreign Affairs Eamon Gilmore has warned there may be serious consequences after voters in Switzerland narrowly backed a proposal to curtail immigration from the EU in a referendum.

Voters in the Alpine nation narrowly backed proposals to curtail immigration from the European Union.

European Union officials have warned that any Swiss restrictions on the free movement of EU citizens would not be acceptable.

Speaking in Brussels today, Mr Gilmore warned that trying to break with the fundamental policy of free movement of people and jobs could have serious consequences for Switzerland.

European partners have threatened to review relations with Switzerland.

The vote was initiated by the right-wing Swiss People's Party and opposed by the government in Bern.

The European Commission said it went against the principle of free movement between the Alpine nation and the EU that has existed for over a decade.

"The EU will examine the implications of this initiative on EU-Swiss relations as a whole," the commission said.

Mr Gilmore described the outcome of the referendum as "very disturbing".

He said he believed the result was a "very worrying development" and one that "will have serious consequences" for the freedom of movement.

He said there was a "growth in the extreme right agenda" across the EU and some of it was "quite xenophobic".

The Tánaiste said it would pose "major difficulties" for the freedom of movement, which is a "cornerstone of what the EU is all about".

Switzerland is not a member of the 28-nation EU, but a pact has ensured the free movement of citizens to and from the union since 2002.

The vote to reintroduce immigration quotas, backed by a razor-thin margin of 19,526 voters, threatens that pact, and with it a key pillar of the Swiss economy, which relies on the EU for nearly one-fifth of its workforce.

Swiss business leaders have been unsettled by the ballot result.

French Foreign Minister Laurent Fabius described the outcome as a "worrying" move that showed Switzerland was withdrawing into itself.

"We're going to review our relations with Switzerland," Mr Fabius told RTL radio.

German Chancellor Angela Merkel's spokesman said that while Germany respected the result, it would create "considerable problems" for Switzerland's relationship with the EU.

Switzerland is home to food and beverage giant Nestle, pharmaceutical companies Novartis and Roche, as well as a host of major commodities dealers, such as Glencore Xtrata and Louis Dreyfus Commodities.

"What's the point of investing in Switzerland, when in the end it's not certain whether you can get qualified staff to carry out your plans," Valentin Vogt, president of the Swiss Employers Association, told the NZZ newspaper.             

He said the vote created toxic uncertainty for Swiss businesses, which already face pressure amid a foreign crackdown on banking secrecy and an outcry over the favourable tax rates some Swiss cantons offer to multinationals.

Swiss banks including Credit Suisse are especially dependent on the flow of foreign workers, employing up to 25% of overall staff from the EU.

"We fear that the pool of available workers will dwindle," said Sindy Schmiegel of the Swiss Banking Association.

"It could become much more difficult for banks to meet their staffing needs."             

Although the Swiss government had urged voters to reject the introduction of EU immigration quotas, it is now obliged to write the results of the referendum into law.

It will have a degree of flexibility as the referendum did not set specific quotas.

Justice Minister Simonetta Sommaruga said last night that the government planned to draft a law by the autumn, before approaching the EU with its plans.

Anger among parties that had opposed the vote was evident today, with the Swiss Liberal Democrats suggesting that Christoph Blocher, the billionaire industrialist and SVP politician who poured his own money into the quota campaign, be sent to Brussels himself to explain the vote.

"He has an obligation to find a good solution, together with the other parties," the FDP said in a statement.

Europe's right-wing parties welcome result

Right-wing parties in Europe have hailed Swiss voters for approving the curbs on EU immigration.

Nigel Farage, the head of the UK Independence Party, Britain's main eurosceptic party, said Switzerland had stood up to "bullying" from unelected bureaucrats in Brussels.

"This is wonderful news for national sovereignty and freedom lovers throughout Europe," said Mr Farage, who is an MEP.

UKIP has led similar calls for a cap on immigration, a touchy issue in Britain since Bulgarians and Romanians were given full rights on 1 January to free movement within the European Union.

UKIP has no representatives in the British parliament but threatens to take vital votes from Prime Minister David Cameron's Conservative party in Britain's next general election in May 2015.

It is also hoping to expand its total of nine MEPs in European elections this May.

France's extreme right National Front party hailed "the Swiss people's lucidity" in a statement, calling for France to likewise stop "mass immigration".

Mainstream media expresses concern

Austria's far-right FPO party said that country would vote the same way given the chance, while Italy's populist Northern League demanded a similar referendum there.

The German newspaper Tagesspiegel said: "With the [Swiss] referendum, it becomes more likely that the anti-Europeans will represent the biggest group in the European parliament, with a quarter of the MEPs."

In France, the business daily Les Echos, described the result as one with "economic consequences that are difficult to predict".

The Belgian newspaper Le Soir noted that "it's the whole scaffolding of Switzerland's bilateral accords with the European Union which is assured of collapse".

Centre-left El Pais, Spain's top-selling newspaper, worried about ripple effects of the vote in an editorial called "Perverse Consequences" published in today’s edition.

"While by a narrow majority [50.3% of votes cast], the victory of those who oppose 'mass immigration' in Switzerland will have consequences for all of Europe," it said.

"Not only does it call into question the agreement on the free movement of people established with the European Union, it also reflects the populist and xenophobic agitation sweeping the Old Continent less than three months before the European elections," it said.

"This is the worst possible outcome for the majority of politicians and Swiss business organisations," it added.

Spanish conservative daily ABC wrote on its website that the outcome of the referendum "caused a real political earthquake in this central European nation and it puts its ties with the European Union in danger".