Relations between the University of Auckland and union members appeared to take a further nosedive last night.

Vice-chancellor Professor Stuart McCutcheon said a letter had been sent to union staff offering a 4.5 per cent pay increase - matching an offer made to non-union staff.

The university was legally prevented from initiating bargaining and making the offer until yesterday, he said.

"The university has offered exactly the same 4.5 per cent salary increase to union and non-union members, because we want to treat all our staff fairly and equitably," said Professor McCutcheon.

But despite yesterday's offer, association staff said the dispute was deepening.

Helen Kelly, general secretary of the Association of University Staff, accused the university of attempting to induce its members into leaving the union.

The association was also angry that the 4.5 per cent offer was made to non-union staff before union negotiations got underway.

The association represents about 30 per cent of the university's 3500 staff.