Image copyright bbc Image caption Scotland can impose tuition fees on students from England, Wales and Northern Ireland

Charging tuition fees to students from the rest of the UK in an independent Scotland could break European law, according to pro-union academics.

EU law prevents undergraduates from European countries outside the UK being charged fees by Scottish universities.

Academics Together - part of the Better Together campaign - said in the event of independence students south of the border would also come under this law.

The Scottish government said the policy was compatible with EU requirements.

Currently Scotland can impose tuition fees on students from England, Wales and Northern Ireland because the EU does not regulate for discrimination within member states.

The Scottish Government's White Paper on independence proposes keeping this if Scotland votes to leave the UK in next year's referendum.

Academics Together urged the Scottish government to publish any legal advice it had received on the issue.

A Scottish government spokesman: "The White Paper is consistent with, and informed by, legal advice the government has received.

The White Paper is consistent with, and informed by, legal advice the government has received Scottish government spokesman

"The content of any legal advice is confidential. By long-standing convention, successive Scottish and Westminster governments have not disclosed the source or content of legal advice other than in the most exceptional circumstances."

'Income loss'

Academics Together is to a publish a report on the issue later.

It will claim that if Scotland leaves the UK, it will be legally obliged to provide free university education to students from England, Wales and Northern Ireland.

It will say: "Even if the numbers of students from elsewhere in the UK stayed at the same level as today, this would represent a loss of income to Scottish universities of £150m.

"If the numbers were to increase - and there would be a very strong incentive for young people from England to come to Scotland for a free education - the effect could be even greater."

The Scottish government would face an extremely steep uphill battle to convince the EU institutions Prof Niamh Nic Shuibhne, Edinburgh University

A government spokesman said the "unique and unprecedented position of a post-independent Scotland" would enable them to continue the current policy of charging tuition fees to students from the rest of the UK, who chose to study in Scotland.

Under European laws, Scottish ministers would need to make an "objective justification" for doing this.

Deputy First Minister Nicola Sturgeon has already told members of Holyrood's European Committee: "We believe that can be done because of the particular circumstances of the geography of Scotland and the rest of the UK, and the policy that exists in other parts of the UK."

The Academics Together report will state "many lawyers disagree" that an objective justification could be made for the policy.

It will quote Niamh Nic Shuibhne, professor of European Union Law at the University of Edinburgh, as saying that "the Scottish government would face an extremely steep uphill battle to convince the EU institutions that it should be entitled to retain a practice involving systemic direct discrimination against one particular cohort of EU citizens".

However, the government spokesman said "very clear legal opinion" on the issue had been published by the universities themselves which "makes clear the possibility of continuing the current system within EU law".