Trenton Oldfield, the protester who leapt into the Thames to disrupt the Oxford v Cambridge Boat Race last year, will not be sent back to his native Australia, an immigration judge said on Monday.

The decision reverses a ruling by the home secretary, Theresa May, that he should be sent back after he was jailed for six months for committing a public nuisance.

Oldfield, 37, an academic and publisher, attended the packed immigration tribunal hearing in London with his wife, Deepa Naik, and their five-month-old baby. He said that because of racism in Australia, his wife and child would not go with him if he was deported and that would be "devastating" to their family.

He broke down in tears as he told how he halted the 158th annual Boat Race in April 2012 out of a feeling of "heartbreak" at the deepening inequality in British society.

"I go round London and see the pockets of deprivation that still exist," he said. "I think I was heartbroken."

Representing the home secretary, Danny Morley said Oldfield's conduct had been in "utter contempt for the law" and he "abused his right to protest in a very public way". Morley added: "He did put himself in danger and others. The whole country saw this and there is a need to be firm against this type of behaviour."

At the end of the hearing, the immigration tribunal judge, Kevin Moore, told Oldfield: "There is no doubt as to your character and commitment and the value you are to UK society generally. It would appear to me from the evidence and the submissions that have been made on your behalf that it would be my intention to allow your appeal."

Oldfield hugged his wife and supporters and said he was relieved at the ruling, which will be handed down formally within 10 days. The hearing drew a crowd of supporters from academia and protest movements. A petition signed by 265 Cambridge academics had urged the tribunal to overturn the home secretary's decision that Oldfield's application to remain in the UK was "not conducive to the public good".

Oldfield told the judge he had targeted the race because it symbolised a society where many people were deprived of opportunities.

He said his plan to disrupt the annual event crystallised after he returned from seven months in Canada looking after his wife's dying father.

"I was vulnerable in terms of realising how short life can be," he said.

He continued: "I realised certain people's quality of life was much better than other people's. When I came back to the UK and saw the poverty and saw the laws the government was passing that were going to make people's lives significantly harder … for no apparent reason, I think I was very emotional.

"I saw the Oxford and Cambridge Boat Race as a symbol of this issue. 70% of the cabinet are Oxbridge graduates."

The wider target, he said was "elitism and the inequality that arises out of elitism".

He likened the protest to boycotts of the Moscow Olympics in 1980 and sporting boycotts targeting apartheid-era South Africa and said "established people" such as David Cameron, John Major and Alan Milburn have all recently spoken out against "entrenched elitism" in the UK.

He had been surprised to be dealt with so harshly by the authorities and had expected "a slap on the wrist" and to be back at home the evening after the action.

He told the court: "I have no desire to be involved in similar actions."