A shock rise of more than 30% over the past year in net migration to Britain to 212,000 has dashed Conservative hopes of meeting their target of bringing the figure below 100,000 before the general election.

The Office for National Statistics said the unexpected rise of 58,000 in the 12 months to last September has mainly been fuelled by migrants from the recession-hit southern European countries of Spain, Portugal, Italy and Greece, as well as Poland.

Net migration to Britain from the EU has doubled in the past year and EU immigration is at the highest level since 1964.

A continuing fall in emigration from Britain has contributed to the rise in the net migration figure, and the ONS said migrants from the latest EU entrants, Romania and Bulgaria, have added 14,000 to the figure before the lifting of transitional controls on 1 January.

This is the third consecutive quarter that the politically sensitive benchmark of net migration – the number coming to live in Britain for more than 12 months minus those leaving to live abroad for longer than 12 months – has risen.

The home secretary, Theresa May, made the Conservative pledge to reduce net migration to the "tens of thousands" by the time of next year's general election the central target of her immigration policy. The chances of meeting that target appear to be disappearing fast.

If the upward trend continues she may leave office with a higher net migration figure than the 244,000 estimated when she became home secretary in 2010.

The Liberal Democrats have consistently disowned the target, stressing it is not coalition policy.

The figures are likely to increase pressure within the Conservative party over the issue of free movement within Europe.

The figures show that 532,000 people migrated to Britain in the year ending last September. The figure includes 60,000 more EU migrants and 25,000 migrants from the rest of the world compared with a year previously. More than 218,000 were students.

A total of 320,000 emigrants left Britain last year, 23,000 fewer than the previous year and the lowest level since 2008, when the number peaked at 427,000.

These factors combined to increase net migration from 154,000 in the year to September 2012 to 212,000 in the year to September 2013.

The ONS figures show that the measures May has taken to curb non-EU migration have bitten quite deeply but have been overshadowed by the rise in migration from within Europe.

Overall figures for non-EU migration show that immigration from outside Europe fell from 269,000 to 244,000. This reflected May's curbs on student migration – the number of those coming to study at further education colleges is down by 34% and the number of overseas students from India has fallen by 21%, and from Pakistan by 55%. The number of family visas granted has gone down by 7,202.

Student numbers rose by 4% in the year to December 2013, with a 7% rise in university students, including a 9% rise in students from China and a 147% increase from Brazil.

Registrations of new national insurance numbers for adults entering Britain rose by 19% to 617,000 in 2013 with the highest increases for those coming from Poland (31,000), Italy (18,000), Spain (14,000) and Portugal (10,000).

Asylum applications rose by 8% in the 12 months to September 2013 to 23,507 with the largest rises from Syria (up 681), Eritrea and Albania.

The London First business group said the figures meant it was "game over" for the Conservatives' "arbitrary" immigration target.

"What we need to be wary of is the government trying to control future figures by further limiting the only number it has power over – non-EU migrants," said Mark Hilton, London First's head of immigration policy.

"In the past this has hit both highly skilled immigrants that we need, as well as foreign students, who are a huge economic asset: higher education is our eighth-biggest export industry, valued at £8bn."

The new immigration minister, James Brokenshire, acknowledged the problem: "The government is ensuring that our controls on accessing benefits and services, including the NHS and social housing, are among the tightest in Europe. We cannot impose formal immigration controls on EU migrants, so we are focusing on cutting out the abuse of free movement between EU member states and seeking to address the factors that drive European immigration to Britain," he said.

Brokenshire stressed that nearly 70,000 fewer migrants were coming to Britain than in 2010 when the government took office.