The economic analysis has reportedly been drawn-up with the support of Home Secretary Amber Rudd (pictured)

The Government's Brexit plans are unlikely to bring net migration below its 100,000 a year target, a leaked study suggested today.

Rules being considered by the Home Office would mean EU workers would need to earn at least £20,500 to come to the UK.

That could reduce inflows from the bloc 40,000 fewer EU migrants coming to the UK annually, according to an impact assessment obtained by the Telegraph.

A tougher system is also being mooted for a 'no deal' scenario with the EU that would mean migrants need to have degrees, a job offer and earn at least £30,000.

Those are the current visa requirements for non-EU workers, and would cut numbers by 90,000 a year.

However, neither option would be likely to bring net migration down to the 'tens of thousands' as pledged by Theresa May.

The most recent figures showed it running at 230,000 a year.

The economic analysis has reportedly been drawn-up with the support of Home Secretary Amber Rudd.

The first option is described as 'flexible migration', and the 'midway point between strict policy and continued Labour mobility'.

The emergence of the study could fuel the row over gloomy analysis of the prospects for Brexit.

A cross-government study leaked earlier this week suggested the economy will take a hit whatever deal is done with Brussels.

UK plc would be up to 9 per cent smaller in 15 years time than if it remained in the bloc, according to the assessment.

But Theresa May today insisted Brexit will go ahead even if Whitehall analysis says it could harm the economy.

The Prime Minister said she would look at forecasts for the impact of leaving the EU but it was crucial the government 'does what the British people want us to do'.

Mrs May also dismissed criticism of her leadership and handling of negotiations, saying she believed a transition deal will be negotiated by March and repeating that she had no intention of quitting.