George Galloway has been accused of racism after walking out of a debate at Oxford University after discovering that his opponent was an Israeli citizen.

The Respect party MP for Bradford West – a vocal critic of Israel and its treatment of Palestinian people – had been taking part in the debate at Christ Church college, speaking for the motion that "Israel should withdraw immediately from the West Bank", when he learned that Eylon Aslan-Levy, a student opposing it, was Israeli.

Galloway interrupted the third-year philosophy, politics and economics student at Brasenose college when Aslan-Levy used the word "we" in reference to Israel.

"You said 'we'," said Galloway. "Are you an Israeli?"

"I am, yes," Aslan-Levy replied.

"I don't debate with Israelis. I have been misled, sorry," Galloway said, standing and putting on his coat, then reiterating as he walked out: "I don't recognise Israel and I don't debate with Israelis."

The Oxford student newspaper Cherwell – which has video footage of Galloway's exit – quoted Aslan-Levy as saying afterwards: "I am appalled that an MP would storm out of a debate with me for no reason other than my heritage. To refuse to talk to someone just because of their nationality is pure racism, and totally unacceptable for a member of parliament."

The debate organiser, Mahmood Naji, told Cherwell.org: "At no point during my email exchange with Mr Galloway's secretary was Eylon's nationality ever brought up or mentioned." He added: "Nor do I expect to have to tell the speaker what his opponent's nationality is."

Galloway said on his Facebook page: "I refused this evening at Oxford University to debate with an Israeli, a supporter of the apartheid state of Israel. The reason is simple: no recognition, no normalisation. Just boycott, divestment and sanctions, until the apartheid state is defeated. I never debate with Israelis nor speak to their media. If they want to speak about Palestine – the address is the PLO."

The incident prompted a flurry of Twitter exchanges, with many people expressing surprise and anger at Galloway's behaviour.

"George, refusing to debate someone because he's Israeli is absurd," wrote Christine Quigley, a former Labour London assembly candidate. "Would you condone if any other nationality?"

She added: "As a former constituent of @georgegalloway and pro-Palestinian, I'm deeply unimpressed he refused to debate someone because he was Israeli."

Another Twitter user, who describes herself as a "proud mum" and "progressive Jew", asked Galloway: "Out of interest would you refuse to meet with a constituent if they had Israeli citizenship?"

Galloway reiterated his earlier points in his replies to his questioners, tweeting: "No recognition of Israel. No normalisation. Christ Church never informed us the debate would be with an Israeli. Simple."

The MP has long been a staunch supporter of the Palestinians and trenchant critic of Israel, speaking of his hatred for the "Zionist state" and calling for its dismantling.

Aslan-Levy told the Guardian he had in fact been calling for a solution that would recognise both states.

"As opposition speaker, my case was not that Israel should remain in the West Bank, but that such a withdrawal should not be immediate – ie unilateral – but in the context of a negotiated peace treaty, which would recognise both Israeli and Palestinian states."

The student moderating the debate also expressed his disappointment at Galloway's actions, and urged him to think again.

Michael Baldwin, a third-year student at New College, noted that Galloway had once been given an honorary Palestinian passport, and said the MP would be "rightly indignant" if someone refused to debate him because of it. He added: "I would encourage Mr Galloway to reconsider his position, which is open to accusations of xenophobia."

A spokesman for the Palestinian boycott, divestment and sanctions campaign moved to distance itself from Galloway's actions, saying the movement rejected "all forms of racism, including Islamophobia and anti-Semitism".

He added: "BDS does not call for a boycott of individuals because she or he happens to be Israeli or because they express certain views. Of course, any individual is free to decide who they do and do not engage with."