The UK will struggle to control immigration after Brexit as it does not have the capacity to measure numbers arriving, leaving, and staying, a parliamentary report has acknowledged.

The report, by the House of Lords Economic Affairs committee, blasted the insufficient information collection, and called for a comprehensive overhaul of the current immigration system, calling it “woefully inadequate”.

The document slams the “flawed” sample surveys used to calculate net migration, which means ministers risks formulating policy “in the dark”.

“The available data on migration are extremely poor. They fail to provide an accurate number of migrants entering or leaving the country or the number of migrants in work”, it reads.

In May 2016, the Office for National Statistics (ONS) was forced to admit European Union (EU) immigration into Britain was nearly 1.5 million higher as previously thought.

The number had been underestimated after “short term” migrants were not properly included in estimations.

The scandal was exposed by Breitbart London, reporting the number of new National Insurance Numbers given to those in work was higher than the number supposedly entering the UK according to the ONS.

The Lord’s report suggests using information from migrant’s tax payments and benefit claims (to gauge how long they stay) and from recently reintroduced exit checks.

“The allocation of National Insurance numbers to overseas nationals can, the ONS acknowledged, ‘provide some useful indication’ about long-term migration”, the report explains.

Furthermore, it says a better way of monitoring international students must be devised, to know how many go home after their studies, and they should not be included in short-term net migration figures.

Commenting on the report, Lord Forsyth of Drumlean, Economic Affairs Committee Chairman, said:

“The Government must have reliable statistics on migration before it formulates new policy, otherwise it will be making crucial decisions – of vital importance to the country’s businesses – in the dark.

The Government issued a response, saying: “We are collaborating with the Office for National Statistics to develop a system which provides a richer statistical picture of EU nationals in the UK.”

The warning comes on the same day the ONS claimed the UK population had hit its largest ever (65.6 million) in 2016 and is projected to continue growing to over 74 million by 2039.

Lord Green of Deddington, Chairman of the think tank, blasted: “Our country is getting ever more overcrowded.

“With three-quarters of our long-term population increase due to immigration, the government absolutely must get the numbers down and soon. The public are getting tired of excuses.”