Two Greenpeace activists who were arrested after attempting to expose embezzlement in Japan's whaling fleet will go on trial tomorrow in a case campaigners hope will spark a domestic backlash against the heavily-subsidised industry.

Junichi Sato and Toru Suzuki were detained in June 2008, two months after intercepting a consignment of whale meat they claimed had been stolen by a member of the crew on the Nisshin Maru, the Japanese Antarctic whaling fleet's mother ship.

The activists – who claimed the meat was destined for the black market – face up to 10 years in prison if found guilty of theft and trespass.

They said the package, retrieved from a warehouse in Aomori, northern Japan, was marked "cardboard" but contained 23kg of salted whale meat worth around 350,000 yen (£2,477).

Greenpeace said it had evidence to prove that at least 23 of the ship's crew smuggled more than 90 boxes of salted whale, disguised as personal baggage, and accused them of defrauding the Japanese taxpayer with the approval of Kyodo Senpaku, which operates the whaling fleet.

Kyodo Senpaku insisted the packages were a "bonus" for crew members who had spent several months in the inhospitable waters of the southern ocean.

Prosecutors, who initially agreed to pursue the embezzlement claims, dropped the investigation on the day Sato and Suzuki were arrested in early-morning raids on their homes.

According to Greenpeace,, Japanese taxpayers contribute an estimated 500m yen to the "scientific" whale hunts each year.

Earlier this month, a UN human rights body condemned the detention of Sato and Suzuki and warned Japan that it had breached several articles of the UN declaration of human rights.

During their 26 days in custody, 23 of which saw them held without charge, the suspects were denied access to lawyers, strapped to chairs and interrogated for up to 12 hours a day.

Their interrogators likened them to members of Aum Supreme Truth, the doomsday cult that carried out the fatal gas attacks on the Tokyo subway in 1995.

Suzuki protested by going on hunger strike for nine days and refusing to talk to investigators for four more.

"They have taken a stand in the public interest," Kumi Naidoo, Greenpeace's executive director, told reporters in Tokyo.

"It has come at a personal and professional cost. To be in detention day after day, tied down, with no lawyer, is a terrifying thing for anyone to endure.

"To have that happen to them when all they were trying to do was draw attention to the abuse of public funds is beyond scary. It is wrong."

Naidoo urged the Japanese prime minister, Yukio Hatoyama, to reopen the investigation into alleged embezzlement by the whaling crew and to ensure Sato and Suzuki were given a fair trial. "The eyes of the world are on Japan," he added.

Since the arrests, more than 250,000 people have signed a petition demanding justice for 32-year-old Sato and Suzuki, 42.

Anti-whaling campaigners have accused the authorities of staging a politically motivated trial, designed to depict peaceful activists as "terrorists", with the eventual aim of closing down Greenpeace's office in Japan.

In an interview with the Guardian after he was released on bail, Suzuki remained unrepentant. "Since my arrest, I have not lied once about what I did," he said.

"But the whalers have had to make up one story after another. Their lies will come back to haunt them."

Two years ago, Greenpeace abandoned its pursuit of the whaling fleet to focus on building an anti-whaling coalition among the Japanese people.

A provision in the International Whaling commission's 1986 ban on commercial whaling permits Japan to conduct "lethal research" into about 1,000 whales in the Southern ocean each year.