Union trustee Fawzi Ibrahim, a former College of North West London lecturer who is standing for the treasurer post, said the UCU needs to halt its repeated overspending.

“We need a three- or five-year plan to work out how we are going to pay back the deficit and get back on a good financial footing,” he said. “We should be budgeting not for a deficit but for a surplus.”

Alan Carr, the incumbent treasurer, said the union had incurred exceptional costs in pensions and redundancies but it was financially healthy for the long term and selling its Britannia Street offices promised to bring in more than pound;20 million.

The UCU spent pound;5m more than its income last year and had budgeted a further pound;1m deficit this year. Mr Carr said last year’s deficit was mainly caused by pension liabilities, which would be paid off over 10 years. It also included pound;1.8m in redundancy payments that came earlier than expected. Mr Carr was now expecting the union to generate a surplus this year.

A move to new offices meant the union had to take a loan of nearly pound;14m, but the debt was cut by the sale of the pound;5.5m Tavistock Place offices of the former Association of University Teachers.

However, interest payments are mounting and repayment depends on also selling the former Natfhe offices in Britannia Street. Mr Carr said the union was already considering offers which could wipe out its debts and generate a surplus if bidders win planning permission.

Mr Ibrahim also criticised the spending on 40 staff redundancies, with an average payout of pound;47,500, saying that many positions were refilled shortly afterwards.