The UK government face an uphill task to reduce the level of immigration by tens of thousands as the latest figures from the Office for National Statistics show that net migration has risen to its highest level in five years.

A sharp fall in the number of people going to live abroad and a resurgence in Polish migrants coming to live in the UK has led to the gap between those arriving to live in the UK for more than 12 months and those leaving to live abroad increasing by almost 100,000 in the year to September 2010, to 243,000.

Overall immigration to Britain has risen by over 9% over the twelve months to September 2010.

The unexpected rise is a major blow to the government’s pledge to drastically reduce the number by the next general election in 2015. Migration experts predict that could now consider even more drastic measures to get the target back on course.

According to Matt Cavanaugh, associate director of the Institute for Public Policy Research, the figures show that the government’s target ‘makes little sense’ and can’t be achieved without damaging Britain’s economy.

‘When they set the target they hadn't planned for emigration continuing to fall. These figures show that emigration of British nationals is down by more than 25% since 2008. This means the government will have to take even more drastic measures to try to meet their chosen target,’ he explained.

Immigration minister Damian Green insisted that the figures cover a period prior to the introduction of the government’s cap on skilled workers and overseas student numbers.

The official figures also show that the Polish community in Britain now numbers 545,000 and is the largest by foreign nationality in the UK, eclipsing the Indian, Pakistani and Irish communities.

Measured by country of birth rather than nationality the Indian community remains the largest though, with many more Indians taking British citizenship.

The figures also show that almost 20% of low skilled jobs are now filled by non-UK born foreign workers, double the number a decade ago. The 666,000 foreign born people working in the UK economy are mainly from other European countries that have freedom of movement.

The detailed figures based on the International Passenger Survey show 310,000 people left Britain to live abroad in the 12 months to September 2010, 50,000 down on the previous year. The 310,000 figure is also 27% down on the peak in emigration from Britain in the 12 months to December 2008 when 409,000 left to live abroad, mainly in Australia and Spain.