The UK government said as quoted by The Guardian that the number of Eastern European workers in the country reached 510 000.

The number referred to citizens of the 10 countries that entered the European Union in 2004.

Self-employed, students and those not working were not included in the count, The Guardian said.

Previous data showed that 427 000 immigrants arrived to the UK since 2004. The discrepancy "helped fuel concerns about foreign workers undercutting British workers' wages, and also a tabloid frenzy about the forthcoming accession of Bulgaria and Romania", The Guardian said.

The news of the restrictions on Bulgarian citizens caused and angry reaction in Bulgaria and the country threatened to impose 'tit-for-tat' restrictions for British.

Minister of state for nationality, citizenship and immigration Liam Byrne said that the government needed to "make progress on… immigration reforms and understand the transitional impacts from the last round of accession in 2004 before… tak[ing] the next step."