* Switzerland to cap residence permits for Romanians, Bulgarians
* Arrivals from those countries have spiked since last year
* Swiss grapple with EU immigration after 2014 vote for quotas (Adds background, comment from Swiss government)
ZURICH, May 10 (Reuters) - Switzerland will curb Bulgarian and Romanian citizens' access to its labour market for the next 12 months, the government said on Wednesday, amid increased migration from those countries after limits were lifted last June.
The Swiss cabinet, whose struggle with immigration from the European Union intensified after a 2014 referendum in which the public demanded that quotas be imposed, will cap the number of five-year residence permits for Romanians and Bulgarians at 996.
While free movement of workers between Switzerland and the European Union is largely guaranteed through bilateral agreements, a so-called "safeguard clause" lets the Swiss impose unilateral limits if migrant numbers exceed certain thresholds.
Workers from Romania and Bulgaria, who have enjoyed freedom of movement since June 2016, topped the threshold last year, with their numbers in Switzerland rising by a net 3,300, about double the increase from 2015.
"Since introduction of full freedom of movement, Romanians and Bulgarian workers have been increasingly coming for seasonal jobs in sectors with higher-than-average unemployment rates," the Swiss cabinet said. "The government is employing one of the tools at its disposal to control migration."
Around 14,330 Romanians and 8,112 Bulgarians live in Switzerland, government data show. Switzerland's population of 8.4 million is about a quarter foreign.
This is not the first time Switzerland has enacted such limits. In 2013, for instance, it applied similar restrictions on eight central and eastern European countries including Hungary, Poland and Slovakia.
On Wednesday, the European Commission said it regretted the latest Swiss move, in particular because the number of EU citizens seeking residency in Switzerland as a whole is actually falling.
Net immigration to Switzerland slowed for a third consecutive year in 2016. Around 143,100 immigrants arrived, down nearly 5 percent from the previous year, while some 78,000 foreigners left, an increase of 5.6 percent.
Romanian State Secretary George Ciamba also said Switzerland's new limits were unfortunate.
"This is taking place in the context of a relatively small number of Romanians who have applied for "B" permits in the last year and runs contrary to the contribution of the Romanian community in Switzerland," according to the Romanian foreign ministry's website, referring to the five-year residence permits.
Swiss-EU ties are being scrutinised for hints of what Britain might expect as it negotiates the terms of its divorce from the EU.
In the wake of Switzerland's 2014 vote in favour of quotas that would have violated bilateral accords with the EU, the Swiss parliament last year dodged a conflict with Brussels by instead adopting a less strict system under which unemployed locals would be given preference when hiring.
The broader issue remains, however, with anti-immigration members of the Swiss People's Party (SVP) pursuing a new referendum to put a halt to free movement of EU workers. (Reporting by John Miller and Silke Koltrowitz; Editing by Michael Shields and Hugh Lawson)