Four people sent back to Vietnam by the Australian Government after trying to flee the country by boat have reportedly been jailed by a Vietnamese court.

Key points: Four former Vietnamese asylum seekers are jailed for between 24 and 30 months for trying to go to Australia

Four former Vietnamese asylum seekers are jailed for between 24 and 30 months for trying to go to Australia Allegations of communist party interference in case

Allegations of communist party interference in case Australian Border Force said Vietnam assured returned asylum seekers would not be punished

According to Voice Australia — a group helping Vietnamese asylum seekers — 42-year-old Nguyen Dinh Quy was sentenced to 24 months in jail and his 39-year-old wife Huynh Thi Kieu was jailed for 27 months for leaving Vietnam without official approval.

Their fellow accused Tran Thi Lua, 37, and 35-year-old Nguyen Minh Quyet were also convicted and jailed for 30 and 24 months respectively.

They were among 46 asylum seekers returned to Vietnam in July last year after their boat was intercepted by an Australian Government ship.

Tran told Radio Free Asia (RFA) before sentencing that both Australian and Vietnamese officials had given the group assurances they would not be punished, before they were returned.

"The Australian Government said that they would return us, and that they and the Vietnamese Government had agreed not to jail us and let us live with our community, but now they treat us like this," she said.

A spokesman for Voice Australia said the four felt cheated by false assurances they would not be punished when they were sent back to Vietnam.

Court documents seen by the ABC allege Tran and the three other accused played leading roles in the attempt to reach Australia, including conceiving the idea, buying a boat, collecting money from other passengers and captaining the boat.

Police allege Tran collected $8,600 for the trip.

Tran Thi Thanh Loan, 46, is appealing a three-year sentence handed to her in April. ( Supplied )

Tran said she had organised the trip because she was searching for a better life for her family.

"Our lives here are so difficult. It is hard to make enough to raise our children," she said.

She told RFA the money raised went towards buying the boat, food and fuel for the trip.

Don An Vo, the lawyer for the four accused, said he was concerned the local government had tried to influence the case.

"The La Gi Township Administration (local communist party) has instructed to punish heavily," Mr Don said in a Facebook post on Thursday.

"The fact that the Township Administration instructed the judicial authorities on the trial is completely against the law."

Three of the accused have been held in prison for varying periods since they were returned to Vietnam last year.

Ms Tran was detained for two months, while Nguyen Dinh Quy has been in custody since last July.

Human Rights Watch said Nguyen Minh Quyet had had a stroke in prison and is unable to move his legs, after being held for a nine-month period.

Official 'told we would be safe from retribution'

Four people had previously been given jail terms for fleeing Vietnam on another vessel, also carrying 46 people, in March 2015.

Tran Thi Thanh Loan, 46, is appealing a three-year sentence handed to her in April, and went to court on Thursday to support those allegedly responsible for the July trip.

Tran Thi Thanh Loan said she had been given assurances she would face no sanctions when returned to Vietnam. ( Supplied )

Her husband — Ho Trung Loi — was sentenced to two years.

She told the ABC through a translator she had been given assurances by an Australian immigration official that they would face no sanctions when returned to Vietnam.

"When we were sent back to Vietnam, a female official — which I believe is from the Immigration Department — told us we would be safe from retribution... and the authorities will help us to reintegrate back to Vietnam and then help us to find jobs," Ms Tran said.

She said a Vietnamese official also repeated the same assurances to the group.

"I and other people were disappointed that the promise was not carried out and now our back is against the wall. I feel like I have been cheated," Ms Tran said.

Ms Tran said she and her family wanted to come to Australia to start a new life, as business conditions were worsening and authorities had knocked down her home when it was part way through construction.

"If I go to jail... I don't know what will happen to my kids. They will be without parents for three years," she said.

Her appeal is yet to be heard.

Vietnam assured asylum seekers would go unpunished

Australian Border Force officials have previously said they were given assurances by Vietnam that asylum seekers returned to the country would not be punished.

In May 2015, Major General Andrew Bottrell told a Senate estimates hearing the Vietnamese Government had put the pledge in writing.

"There was an engagement with the Vietnamese and... an assurance from the Government of Vietnam that there would be no retribution for their illegal departure from Vietnam," he said.

When asked for comment on Thursday, a spokesperson for the Department of Immigration said any potential criminal investigations or proceedings for people-smuggling-related offences were a matter for the Vietnamese Government.