The University and College Union has been criticised for donating £2,000 to a Palestinian charity whose trustees include the head of the union's international department.
The union made the contribution to the Friends of Birzeit University (FoBZU), a UK-registered charity of which Paul Bennett is a trustee. Birzeit is a Palestinian institution that is based in the West Bank.
"It seems to me that there is a conflict of interest," said Lesley Klaff, a senior lecturer in law at Sheffield Hallam University, who said she had resigned her union membership in protest over the donation.
"My search of the FoBZU charity has also revealed that their charitable status was granted for the purpose of education/training and yet the UCU is giving them money for 'housing and transportation' costs."
A spokesman for the UCU's head office said: "Paul worked closely last year with FoBZU on behalf of UCU, trying to arrange speakers for UK debates, something that cost FoBZU considerable time, money and effort.
"This was done at the request of the UCU general secretary, who was aware of Paul's connection with FoBZU, and indeed was glad to be able to make use of the link. UCU felt the £2,000 donation was appropriate to recompense FoBZU for the money it spent and its time and efforts."
The issue is particularly sensitive as the UCU prepares to debate a highly controversial motion at its annual conference next month, which raises the issue of an academic boycott of Israel's universities.
The motion, backed by the union's president, Linda Newman, asks the union to use testimonies of UCU delegates to Palestine to "promote a wide discussion by colleagues on the appropriateness of continued educational links with Israeli institutions".