Management at the National Union of Students (NUS) denied claims that it has launched a "fundamental attack" on its staff's trade union rights.

Bosses want to standardise conditions for all staff including maternity pay, childcare, contracted hours, holidays, overtime and sickness rules.

The plan for compulsory standardisation was scrapped after staff union Unite opposed the move because some staff could lose benefits it has previously negotiated.

But chief executive Ben Kernighan made public on Monday plans to offer the new conditions to staff "voluntarily."

Student trustee Gordon Maloney called the move a "fundamental attack on our staff's right to organise."

He said it made the "recognition agreement between NUS and the staff trade union meaningless" and that introducing a voluntary scheme made strike action against it illegal.

Interim policy and research director Hilary Carter insisted yesterday that "the decision by the board does not attempt to undermine staff."

She said: "Trustees decided to protect those staff who wanted to stay on the same terms and condition by making a voluntary offer.

"The voluntary move means that those staff who choose to change terms and conditions will benefit from significant improvements."

University of the Arts Students' Union president Shelly Asquith said the dispute was "ironic" when NUS is encouraging unions to support striking university and college workers next week.

"It sounds as though we need to support our own staff a bit more too," she said.