A surge in immigration from Romania and Bulgaria and a drop in people leaving the UK has dealt another blow to Government hopes of slashing net migration to the tens of thousands.
Migration experts and rival politicians accused the Conservative-led Government of losing its grip on immigration policy as official figures revealed the net flow of migrants into the UK surged year-on-year by more than a third to 212,000 in the 12 months to September 2013.
A "statistically significant" leap in the numbers of Romanians and Bulgarians was partly behind the rise, as 24,000 citizens from the eastern European countries arrived in the UK in the period, nearly three times the 9,000 in the previous year.
And a huge increase in numbers arriving from across the whole European Union (EU), over which the Government has much less influence, underlined the difficulties faced by Prime Minister David Cameron and Home Secretary Theresa May in slashing net migration to below 100,000 by the 2015 general election.
Ministers conceded no formal immigration controls can be imposed on EU migrants but insisted efforts were being made to cut out abuse of free movement in the region.
However, in a rare speech to both Houses of Parliament in the royal gallery of the Palace of Westminster, German Chancellor Angela Merkel hailed free movement as " one of the greatest achievements of European unification" in a sign any renegotiation will be a mountain to climb for the Government.
Experts at the Migration Observatory at the University of Oxford said the figures from the Office for National Statistics (ONS) suggest it is "extremely unlikely" the Government will now hit its migration target.
"The key changes in this report are to EU migration - an area over which immigration policy has less direct influence," Scott Blinder, director at the Migration Observatory, said. " This highlights the fact that the net migration target is not something that can be delivered purely through policy, but relies on other trends as well."
Some 532,000 people immigrated to the UK in the year ending September, up from the 497,000 people who arrived during the previous year, while 320,000 emigrants left the country, down from the 343,000 the previous year.
EU citizens arriving in the UK has driven the increase, rising to 209,000 from 149,000 the previous year, while s ome 65,000 citizens of so-called EU15 countries, that is pre-2004 members of the union, arrived to work in the UK in the period, an increase of 23,000 year-on-year.
Romanian and Bulgarian citizens arriving for work-related reasons in the same period stood at 17,000, of which 11,000 reported having a definite job, the ONS said, up from 2,000 the previous year.
The two eastern European countries joined the EU on January 1 2007. Since then, migrants from Bulgaria and Romania coming to the UK were subject to transitional employment restrictions, which placed limits on the kind of employment they could undertake - such as self-employed status or skilled work.
However, these restrictions ended on January 1 this year, giving unfettered access to the UK labour market.
Against a backdrop of growing concerns of an influx of Romanians and Bulgarians to the UK, and a surge in popularity for the UK Independence Party (Ukip), the Prime Minister last year unveiled a series of tough measures designed to clamp down on abuse of free movement between EU member states.
Sir Andrew Green, chairman and founder of campaign group Migration Watch UK, which has predicted the arrival of 50,000 Romanians and Bulgarians each year for the next five years, said: " The figures also show that net migration from Romania and Bulgaria was about 20,000 in the year to last September, even before the restrictions were lifted. We believe this confirms our estimate of 50,000 a year over the next five years."
The number of National Insurance numbers given to foreigners - an important indicator of immigration levels - showed a 19% rise to 617,000 in 2013.
There were also large increases in the number of citizens of crisis-hit eurozone countries, such as Portugal, Italy and Greece.
Shadow home secretary Yvette Cooper said: "These figures show the Government's net migration target is in tatters, and their immigration policy is a mess."
Immigration of non-EU citizens saw a statistically significant decrease to 244,000 in the period, down from 269,000 the previous year.
Statisticians said this was due to fewer New Commonwealth citizens - such as those from India - migrating to the UK for formal study.
Immigration and security minister James Brokenshire, who recently took on the role after Mark Harper MP stepped down amid controversy surrounding the immigration status of his cleaner, said: "Uncontrolled, mass immigration makes it difficult to maintain social cohesion, puts pressure on our public services and forces down wages for people on low incomes."
He added: "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."
However, the drop in non-EU citizens is likely to fuel fears that Britain is being perceived as "closed for business" by foreign students who are seen by many as valuable to the British economy.
Mark Hilton, head of immigration policy at business membership organisation London First, said limiting non-EU migrants had previously "hit both highly-skilled immigrants that we need, as well as foreign students, who are a huge economic asset".
Ukip leader Nigel Farage said: " These latest figures show just how out of control the Government is when it comes to controlling immigration in and out of the UK. It is utterly pointless setting immigration targets when you can't even decide who comes into this country."
Liberal Democrat Business Secretary Vince Cable said: "Today's figures are good news for British workers. As our economy recovers, fewer people are choosing to emigrate as they see more job opportunities at home. In fact the number of people in work is at an all-time high and rising fast.
"What is striking about the employment figures is that, contrary to popular myths, 90% of British jobs being created are going to British workers. This shows how important it is for employers and Government to continue investing in skills and is good for the economy and our society.
"This is further proof that any quota on migration, such as the one Conservatives are pushing to get net migration down to tens of thousands, is unworkable and contradicts our aims of getting Britain back on its feet."