A trustee of the National Union of Students (NUS) has accused the organisation's chief executive of a "fundamental attack" on its staff's right to organise and strike.

NUS Scotland president Gordon Maloney slammed chief executive Ben Kernighan on Tuesday for taking a "belligerent and anti-union" approach to talks over contract changes.

Mr Maloney was replying to an email sent to student union presidents by Mr Kernighan on Monday through a publicly accessible list.

The email revealed details of an ongoing dispute over the proposed "harmonisation" of terms and conditions for all NUS workers.

It outlined how changes were rejected by the staff trade union following negotiations and a meeting with employment disputes service Acas last week.

Mr Kernighan added that NUS was now going to "offer employees a voluntary move to a set of new terms and conditions."

He claimed the move would "not affect the terms and conditions of any employee who chooses not to take up this offer."

But Mr Maloney explained making the scheme "voluntary" prevented staff legally from taking strike action.

And he said: "This is a fundamental attack on our staff's right to organise.

"Staff are not only being asked to move onto new terms and conditions, but actually onto a whole new legal employer - rendering the recognition agreement between NUS and the staff trade union meaningless.

"It is clear that the failure of these negotiations was pre-empted and leaves the distinct impression that the negotiations were not done in good faith."