- Net migration is the difference between numbers entering and leaving Britain
- 23,000 fewer people than expected have stayed in the UK at end of 2012
- 176,000 migrants entered UK in the year to December 2012, up from 153,000
The Government's attempt to slash net migration has suffered a serious setback today after official figures revealed the first increase in more than a year because too few people left Britain.
Home Secretary Theresa May and Prime Minister David Cameron want to reduce the difference between those leaving and entering the UK from non-EU countries to less than 100,000 before 2015.
But the Office for National Statistics (ONS) revealed a net flow of 176,000 migrants came to the UK in the year to December 2012, up from 153,000 in the year to September 2012, ending five consecutive quarters of decline.
Picture of Britain: Net migration is up after more people entered Britain than left, official figures revealed
The ONS also revealed the number of children born in the UK to Romanian mothers has reached a record high as the country became one of the top 10 places of origin for foreign-born mothers for the first time.
The figures come amid growing concern that Britain will face a new wave of eastern European immigration when access restrictions to the UK labour market for Romania and Bulgaria are lifted on January 1 next year.
Chris Bryant MP, Labour's shadow immigration minister, said: 'The Prime Minister promised 'no ifs and no buts' to get net migration down to the tens of thousands by the end of the Parliament.
'But these figures show an increase in immigration over the last three months, with more EU migrants arriving.'
Allowed to visit: This graph shows the number of visas issued to people from the main world regions
The increase was driven by a drop in the number of migrants leaving Britain, which fell from 351,000 to 321,000, while the number of immigrants arriving in the country also fell from 566,000 to 497,000.
There has been a 'statistically significant' decrease in the net migration of citizens from outside the European Union (EU) to 157,000 in the year ending December 2012 from 204,000 the previous year, the ONS said.
Disappointment: A Tory pledge to reduce migration has faltered because figures show the over number has risen slightly as fewer British and EU citizens emigrated from the country
This was driven by a drop in immigration of non-EU citizens, particularly in the number of citizens of New Commonwealth countries, which includes African countries such as Botswana, Kenya and Malawi and Indian subcontinent countries such as Bangladesh, India and Pakistan.
The drop in New Commonwealth citizens immigrating to the UK - from 151,000 in the year ending December 2011 to 97,000 in the year ending December 2012 - is as a result of fewer people arriving to study in the UK from those countries.
Sarah Mulley, associate director at the Institute for Public Policy Research (IPPR), said: 'Today's statistics suggest the Government is running out of options to meet its target to reduce net migration to less than 100,000 by 2015.
'Recent declines have been driven in large part by falling numbers of international students, which has come at a high economic cost, but this trend now appears to be levelling off.
'The Government cannot further reduce student numbers without imposing even more significant costs on the education sector and the UK economy.'
Dr Scott Blinder, acting director of the Migration Observatory at the University of Oxford, said: 'This is a mixed outcome for the Government in its plans to cut net migration to the 'tens of thousands'.
'On the one hand net migration is still down on 2011, but the recent increase shows that this downward trend is not reliably consistent and still depends partly on emigration of British citizens.'
A total of 58,000 immigrants arrived from countries which joined the EU in 2004, including Poland, the Czech Republic and Lithuania, down from 77,000 the previous year.
The number of immigrants arriving for study in the UK is now similar to the estimated number of people arriving to the UK for work, the ONS said.
Around 180,000 immigrants arrived in the UK for formal study in the year to December 2012, compared to 232,000 the previous year.
Why they came: The majority of people coming into Britain were here for work or to study, statistics show
Elsewhere, the ONS revealed, in 2012, one in eight or 12.4% of the resident population of the UK were born abroad, compared to one in 11 or 8.9% in 2004.
And in the same period, one in 13 or 7.8% of the resident population of the UK had non-British nationality, compared to one in 20 or 5% in 2004.
India was the most common non-UK country of birth in 2012, with 729,000 residents of the UK born in India, while
Polish was the most common non-British nationality in 2012, with 700,000 residents of the UK having Polish nationality.
And in another pack of data, the ONS revealed a quarter of births - 25.9% - in 2012 were to mothers born outside the UK which was a slight increase from 25.5% in 2011.
Poland remains the most common country of birth for non-UK born mothers in 2012, while Romania moved into the top 10 most common countries of birth for non-UK born mothers in 2012, replacing China.
Pakistan remains the most common country of birth for non-UK born fathers in 2012.
Immigration minister Mark Harper said: 'Immigration from outside the EU is now at its lowest level for 14 years.
'At the same time, there has been an increase in the number of sponsored student visa applications for our world-class universities, and an increase in the number of visas issued to skilled workers.
'We are committed to bringing net migration down from the hundreds of thousands to the tens of thousands.'