Oxford University Student Union announced it was leaving the NUS on 21 May after students voted by a majority of just 128 votes to ditch the national body.
However, it has emerged that about 1,000 votes cast in favour of the “No” to reaffiliation – which received 1,780 votes in total – may have been faked.
According to evidence submitted by Jack Matthews, who led the No campaign, the 1,000 spare unique voter codes were used “in large clusters…at a similar time” and that the votes all came from log-ons at the same IP address.
His complaint also claims that a “significantly larger number” of unique voter codes than normal were issued, with about 23,000 codes issued for an electorate of around 21,500, of whom 15 per cent voted.
Mr Matthews, president of the Oxford University Conservative Association, had led the campaign for Oxford to leave the NUS, saying it needed to change. He previously accused it of left-wing bias.
An OUSU committee has now overturned the result of last week’s NUS referendum, which means the union is likely to remain affiliated to the national union.
Returning officer Alexander Walker, a student at Wadham College, has resigned, saying his position was “no longer tenable” as “the grave situation with the NUS Referendum happened under my watch”.
OUSU’s operations and events manager, Tom Rutland, acting returning officer, will now bring a motion to the union’s council to re-affiliate, suggesting there will not be a further poll.
“I will be bringing a motion to 7th Week OUSU Council to reaffiliate to National Union of Students, given that without 1000+ false ballots for ‘NO’, the result would have been 70-30 YES – a margin of more than 2:1,” he said.
A university spokesman said: “The proctors are aware of the complaint made to OUSU and are monitoring developments.”