The Labour leader was asked whether he believed that Soleimani had engaged in acts of terrorism before he was killed in a US air strike last week.
Speaking to Sky News, Mr Corbyn was given four opportunities to label Soleimani a terrorist – but refused to do so on each occasion.
When asked why Soleimani was in Iraq, Mr Corbyn said: “He was in Iraq, for reasons of contact, I assume, with the Iraqi government – I've no idea what his actual meetings were.
“All I'm saying is that to assassinate an official of a foreign government in a third country, in this case Iraq, is illegal under any law and the US – if it wants the world to stand by international law – must stand by international law itself.”
Asked again if he accepted that Soleimani was a terrorist, Mr Corbyn responded: “I'm not here to defend the special forces of Iran, I'm not here to defend any of those actions that have happened or been planned for the future.”
Mr Corbyn was then asked if he agreed with Boris Johnson’s assessment that Soleimani was a terrorist, and responded by criticising the prime minister for not appearing in Parliament on Tuesday to answer questions about the incident.
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On the fourth question, which directly asked if Soleimani was a terrorist, Mr Corbyn said: “Soleimani is the head of special forces of Iran. They obviously operate in all kinds of places that you or I would not agree with or want. That is not the point.”
Mr Corbyn has described the US assassination of Soleimani as “illegal” and wrote to Mr Johnson to demand answers.
The outgoing Labour leader has previously been criticised for being paid to appear on Iran’s state television broadcaster Press TV.
He was met with laughter as he told MPs on Tuesday that he had “long spoken out against the Iranian government's human rights record”.
Mr Corbyn said the killing of Soleimani – that has resulted in Iran firing rockets at bases in Iraq housing US troops – was “an extremely dangerous and aggressive act that risks starting yet another deadly war in the Middle East”.
The US has insisted the strike was justified on the grounds of self-defence.