Chancellor George Osborne has unwittingly admitted that the government will miss its immigration targets by a significant margin.

The UK Treasury released figures today suggesting that each British household would be £4,300 “worse off” if Britain leaves the European Union (EU).

However, campaign group Migration Watch UK has pointed out the Treasury’s forecast uses figures that assume immigration will be far higher than the government promised.

Chairman Lord Green of Deddington said: “The Treasury Forecast takes the [Office for National Statistics] principal population projection that has a long term assumption that net migration will be 185,000 from 2021. In other words, it assumes that the government will miss their immigration target by a country mile and we will, on the official projections, see an increase in the UK population of six million over the next 15 years.”

Prime Minister David Cameron has consistently promised to reduce net migration to the “tens of thousands” since he took office in 2010, but has missed this target every year with immigration continuing to rise.

A large contributing factor to the UK’s rising immigration is the number of EU migrants over whom the government has little control thanks to Britain’s EU membership.

“Given that no serious commentator believes that the ’emergency brake’ will have any significant effect, the government should also explain how even this very unsatisfactory outcome could be achieved with no limits on EU migration, which is now running 170,000 a year out of 330,000,” Lord Green added.

He also highlighted the benefits that could come from reducing migration from the EU, something that could only realistically be achieved by leaving the bloc.

“A reduction in low-skilled migration from the EU could improve productivity, public finances and [gross domestic product] per capita as well as raise wages and reduce pressure on housing.”