Theresa May has yet again reiterated that she is determined to ensure that non-EU students leave the UK on completion of their course.
In an article for the Sunday Times, Mrs May wrote: "The gap between the number of non-EU students coming to this country and departing each year is 96,000 - half the net migration from beyond the EU."
She also argued that Europe’s Schengen Visa system was “broken”, saying that EU migrants will have to show they have a job lined up before they are allowed into the UK.
However Ex-universities minister David Willetts has slammed Mrs May's suggestion calling the figure not a solid basis for policy.
Mr Willets, told the BBC Radio 4, “"People who come here to study should study, perhaps do some post study work and then go back to their country.
"We are selling them a service, we reap a lot of benefits from that, but studying in Britain is not and should not be a means to settlement.
"My disagreement I'm afraid is that the particular figures that were being cited … for number of students staying on is very unreliable.
"It is a widely disputed and doubted figure and would not be a solid basis for policy."
Mr Willetts said the information was provided by the International Passenger Survey (IPS), but had been questioned by bodies including the Commons Public Accounts Committee.
"I don't think it is a reasonable indicator. It is based on a survey - by the time you get down to the number of students - of a few hundred students," he said.
The former Tory MP further said that in some cases people were recorded as students when they arrived but classed as workers when they left. Other "better and more reliable" research by the Home Office between 2007 and 2012 indicated just 2% of students failed to comply with their visa requirements.
The former MP reportedly added, "My view is that the vast majority do leave," he said. "I don't know why she is using these figures, if she is going to rely on them ...
"Of course they are in circulation, but they must not be used as is a basis for policy.
"It is not the case that out of the 150,000 or so overseas non-EU students who come to Britain every year 100,000, two thirds, of them suddenly breach all their visa conditions and stay on for many years.
"There is no reliable evidence that suggests that is actually happening."