Sprent Dabwido, the former president of Nauru who spent the last few years fighting persecution from the new government, has died in Australia at the age of 46.

Dabwido had spent his last few weeks in Armidale, New South Wales, with his wife, Luci, after seeking asylum in Australia and getting treatment for terminal cancer.

He was president of Nauru from 2011 to 2013, and was re-elected to parliament in 2013. However, the following year he was suspended from the parliament by the current Waqa government, alongside other opposition figures.

In recent years he has repeatedly spoken out against the Waqa-led government, and said he regretted signing a deal with the then Australian prime minister, Julia Gillard, to restart offshore processing on Nauru. He said the deal had led to deaths of asylum seekers and refugees on the island, and had bred corruption and greed.

“It is time to end processing on Nauru,” he told SBS in March. “It is hurting Nauru as much as it is hurting Australia – it has turned my island upside down.”

The Waqa government has been found to operate an unwritten blacklist against Dabwido and others. Dabwido and supporters have repeatedly alleged their passports were withheld preventing travel – in Dabwido’s case for medical treatment.

A statement on Wednesday from Dabwido’s friend and the country’s former foreign minister, Mathew Batsiua, said Dabwido was diagnosed with nasopharyngeal cancer in April last year, but that he was denied government-funded overseas medical treatment.

“The Nauru government refused us passports despite a request from myself and others to visit Sprent before his death,” Batsiua said. “The government prohibited us from attending a recent commitment ceremony with his partner Luci in Sydney, but we stayed in contact through the phone and social media.

“I can say Sprent died the way he lived. He was brave, outspoken and always kept his sense of humour, even in the worst times. Sprent was a truth teller until the end. He also died happy, surrounded by people who loved him.”

Dabwido was seen as the leader of a group known as the Nauru 19 – Nauruan nationals including former ministers who were charged over anti-government protest in 2015. The protests were in response to the expulsion from parliament of three MPs who had criticised the government in media interviews.

In the subsequent years the cases went in and out of court as the government sought increased sentences for those who had pleaded guilty, maintained its prosecution of others, and quietly withdrew from a treaty which established Australia’s high court as Nauru’s highest court of appeal.

Last year an independently appointed judge, Australian Geoffrey Muecke, ruled the group had no prospect of a fair trial as the government wanted to see them jailed for a long time and was “willing to expend whatever resources, including financial resources, as are required to achieve that aim”.

He said the government’s actions were “a shameful affront to the rule of law”.

Muecke also determined clear evidence of a government-operated blacklist against members of the group.

The case remains a live issue, with the newly created appeal court hearing an attempt to have Muecke’s judgment thrown out.