PARLIAMENT's failure to guarantee European Union citizens the right to stay before Brexit talks has thrown into doubt the future of thousands of Oxford academics, it is warned.

Some foreign staff have already left as a result of current uncertainty and many more were now likely to consider their positions, two college heads told The Oxford Mail.

Their comments came after the House of Commons – including Oxfordshire's five Conservative MPs – rejected calls to guarantee the rights of EU citizens to remain in the UK by 273 votes to 135 on Monday.

The reason given for the decision was to ensure there were 'no strings attached' when negotiations start.

The House of Lords originally suggested the amendment to the Government's bill – designed to give Theresa May the power to trigger Britain's formal exit from the bloc – but peers later voted not to challenge MPs over the issue again.

It was despite a letter from 38 Oxford colleges and Oxford University's Vice-Chancellor, Professor Louise Richardson, warning Parliament that leaving EU citizens in doubt of their status could do 'enormous damage' to research.

In a statement afterwards, the university said it was 'disappointed but not surprised' MPs chose to reject the amendment.

A spokesman added: "We will continue to press for an early resolution of this issue and for reciprocal arrangements for UK nationals in the EU."

With the Brexit bill expected to gain royal assent today, Theresa May is free to trigger Article 50 of The Lisbon Treaty and fire the starting gun of negotiations.

The Prime Minister has promised to do so before the end of the month and said the status of EU nationals – and Britons living in member states – will be a priority issue.

But Professor Steve Cowley, a world-renowned theoretical physicist and president of Corpus Christi College, warned continued uncertainty was already damaging Oxford and the UK's attractiveness to the scientific community.

He added: "It is going to be diminished if we do not move quickly to assure people we are open for business.

"The Brexit talks are potentially going to take place for several years and in that time you can dismantle an awful lot of very valuable things, so the Government has got to start putting forward solutions.

"There is a significant number of people now thinking that being here is not the best move for them right now, because there is too much uncertainty."

Hertford College principal Will Hutton, former editor-in-chief of The Observer, said: "The university and colleges together employ thousands of EU nationals in various capacities and they are all carrying in their minds that there is a risk.

"Many researchers work on the basis of a series of renewable contracts and there can be some months between one contract and another. Will they be required to go home to their native country in that time, or will they be allowed to stay?

"And if a parent is an EU national, what will happen to their children?

"We thought it was better to not have these issues as part of the negotiations, but the Government has not taken that stance.

"It will not be cost-free, because there are all kinds of concerns people have that are not allayed."

Speaking to a House of Commons committee on Wednesday, Brexit Secretary David Davis insisted a good outcome from exit talks with the EU was 'eminently achievable'.

He told MPs: "From talking to member states' foreign secretaries, finance ministers and prime ministers, there is a growing determination to get a constructive outcome.

"That desire, that wish, that commonality of culture and commonality of interest, is what I think will drive this in the long run, rather than any negotiating gambits we use."