Net migration to the UK could increase by more than 100,000 under its government's post-Brexit plans, a new report claims.

The measure - the difference between the numbers arriving and departing- could reach 380,000 a year if the proposed new system is introduced, according to campaign group Migration Watch UK.

This would be higher than the record figure of 336,000, which has been registered three times, most recently in the 12 months to June 2016.

The latest statistics put net long-term international migration at an estimated 273,000 in the year to June 2018.

Migration Watch UK said its calculations would mean a rise of more than 50pc compared with the current 10-year average of 250,000 a year.

But the Home Office described the report's claims as "inaccurate and untrue".

Following repeated delays, ministers finally presented details of the biggest shake-up of the immigration regime for more than 40 years shortly before Christmas.

Under the proposals, a new route will be created for migrants at any skill level to come to the UK temporarily, the annual cap on skilled work visas will be scrapped, and employers wanting to sponsor overseas employees will no longer be required to carry out a "resident labour market test".

The report from Migration Watch UK, which campaigns for tighter immigration controls, said: "Far from reducing immigration to sustainable levels as the Home Secretary has claimed, these white paper proposals are likely to see net migration rise by over 50pc.

"Furthermore, the migrant inflow will include a far greater proportion of non-EU migrants than is currently the case.

"In effect, EU migrants would be replaced - and more - by migrants from the rest of the world.

"The Government claim that their policy will restore sovereign control of our borders.

"In reality it will lead to higher levels of immigration, including a higher proportion from outside the EU."

The calculations are based on a number of assumptions about future inflows and outflows.

The paper estimated that "net foreign migration" would be about 435,000, comprising 90,000 from the EU and 345,000 from the rest of the world.

Taking into account average net emigration of UK nationals of 55,000, overall net migration could stand at about 380,000 a year, the report claimed.

It said the estimates ignored a proposed temporary route for short-term work, which would allow nationals of specified countries to come to the UK for a maximum of 12 months.

Official statistics define long-term migrants as those who move to a country other than that of their usual residence for a period of at least a year.

In response to the Migration Watch UK report, a Home Office spokesman said: "These remarks are inaccurate and untrue.

"Skilled workers will be required to meet a minimum salary threshold, which the Migration Advisory Committee recommend should be set at £30,000.

"We will be engaging with business on this, but it ensures we can attract the talented people we need for the UK to prosper while controlling immigration.

"Furthermore, the proposed temporary short-term workers route, designed to help businesses adjust when the future immigration system comes into effect in 2021, will be reflected in official migration statistics.

"We are ending free movement and through the future system we are committed to bringing net migration down to sustainable levels and keeping the border secure."

Online Editors