A B.C. husband and wife are facing 10 years to life imprisonment in China for allegedly under-reporting the value of wine they export to that country. And the Canadian government is under fire for not doing more to help them.

Chinese customs officials in Shanghai have charged John Chang, 62, and his wife Allison Lu with smuggling. Their trial is scheduled to begin May 26.

Both have been under arrest since March 2016. Chang has been in jail since then. Lu was held until January, but was forced to surrender her passport and is barred from leaving China.

Push for PM intervention

Lawyers and politicians lining up behind the couple describe their detention as outrageous, excessive and a gross violation of personal liberty and security.

Lulu Island winery owner John Chang is facing trial in China for allegedly under-representing the value of his wine. (Lulu Island Winery)

They're pushing the federal Liberal government to intervene immediately, claiming Chang's physical and mental health is deteriorating behind bars.

Chang and Lu operate Lulu Island Winery. According to the company web site, it is the largest winery in Richmond, B.C., producing "table wines, fruit wines and…ice wines."

Before the couple's arrest, the winery claimed its exports accounted "for almost 20 per cent of all Canadian wine exported to China."

Last July, Chinese state-run media showed boxes of Lulu Island wine being examined by customs officials, and reported "a certain brand of ice wine in Canada" had been declared at around 10 Yuan a bottle (under $2 Cdn), when it was worth many times that amount.

On Friday, Gerry Ritz, Conservative international trade critic, raised the case during question period in the House of Commons.

Assault on rights, says MP

"The arrest of Mr. Chang and Ms. Lu for a fabricated customs violation is an assault on their basic rights, a breach of China's international trade obligations and China's own customs laws," Ritz told fellow MPs.

Ritz called on the prime minister to intervene, but Justin Trudeau was away on a tour of B.C.

In his absence, Omar Alghabra, parliamentary secretary to the minister of foreign affairs, responded.

"We are following this case very closely," Alghabra said. "We are in constant contact with Chinese local authorities … we will not stop until we resolve this matter."

Chinese customs officers inspect boxes and bottles labelled with the Lulu Island Winery logo in photo supplied by Chinese state-controlled media (Legaldaily.com.cn)

The couple's daughter, Amy Chang, 23, has been running Lulu Winery since her parents were arrested.

"This has been a very difficult and emotional year for me," Chang wrote in a May 19 press release. "As a Canadian company and as Canadian citizens, we have let the Canadian government take the lead on resolving this issue." She added the allegations "are without merit."

On Parliament Hill, Ritz claimed the Trudeau Liberals are mishandling the case by treating it as a consular issue, instead of a serious trade dispute.

"The family and the Changs deserve a lot better from the government," he told MPs. "They constantly get this consular issue dribble that really gets no results. (Chang) has had three visits in the past 13 months from consular officials. That is just not good enough."

A government briefing prepared by lawyers retained by the couple's family is also critical of the Trudeau government.

Lulu Island winery owner John Chang was invited on a China trade trip in 2014 with then-prime minister, Stephen Harper. (Office of the Prime Minister)

"Lulu Island winery is not aware of any progress or activity to date by the Canadian government in holding China customs to account," said the briefing, written by the Fasken Martineau law firm. It was delivered to Global Affairs ministry officials earlier this month.

The briefing describes the arrests of Chang and Lu as "outrageous and unconscionable … a gross violation of personal liberty and security."

The briefing paper hints the couple became a target of Chinese wrath because they maintained their innocence.

"Many other foreign wineries…were similarly charged but released shortly after admitting to the under–reporting and paying…fines." it says. "Mr. Chang and Ms. Lu denied violating Chinese rules and were subsequently denied bail."

The briefing paper also warned that the conviction rate in China for criminal offences is nearly 100 per cent.