After EU expanded to include 10 Eastern European countries, with the exception of the UK, Ireland and Sweden, all other pre-2004 EU member states decided to temporarily restrict labour market access to migrants from the 8 countries who joined the EU upon their accession to the EU in 2004. This was possible because the accession agreements allowed member states of the EU to impose restrictions on the immigration of citizens from the new member countries for a maximum of seven years. In the UK, citizens from those countries were able to freely and legally take up employment from May 2004.

The UK government predicted that it would only be 15000 people per year moving to the UK. However, in the first quarter of a year after accession, 42000 moved to the UK to work. By 2006, an estimated 600 000 people had migrated to the UK.

At the time, 7 out of 10 migrants from eastern Europe came from Poland, while the largest group were Slovakian. They were aged 16-39, which resulted in a mini baby boom (between 2004 and 2008, births increased by over 60 000). These migrants found jobs all across the UK, in factories, warehouses and as packers.

Half of all EU nationals coming to the UK in 2015 were nationals of accession countries. In 2016, the number of eastern European migrants working in Britain has surpassed 1million for the first time. Figures revealed that the number of workers from eastern European nations, including Poland and the Czech Republic, was four times higher than a decade ago, when the number stood at just over 250,000.

In 2015 the polish government launched a campaign called Returns, to encourage the hundreds of thousands of workers who moved to the UK to return home amid fears a brain drain is leaving the country short of talent.