The Reading University Atheist, Humanist and Secularist Society (RAHS) said they wanted to celebrate free speech and promote their upcoming debate 'Should we respect religion?'
But they were ordered to remove the offending fruit by union staff who said their actions were causing 'upset and distress' to a number of Muslim students and other societies.
RAHS refused, citing that they had labelled the pineapple after the Islamic prophet to 'encourage discussion about blasphemy, religion, and liberty'.
A spokesman said: 'We wanted to celebrate the fact that we live in a country in which free speech is protected and where it is lawful to call a pineapple by whatever name one chooses.'
They claimed the union then issued them with the ultimatum: 'Either the pineapple goes or you do.'