Paul Whelan, a former US Marine accused of espionage and arrested in Russia, listens to his lawyers while standing inside a defendants' cage during a hearing at a court in Moscow on January 22, 2019. (Photo by Mladen ANTONOV / AFP)
Washington CNN  — 

Paul Whelan, a US national detained in Moscow’s Lefortovo prison on espionage charges, has now been behind bars for 300 days as a judge once again extended his pre-trial detention until Dec. 29, according to US embassy spokesperson Rebecca Ross and Russian state media TASS.

“300 days in Lefortovo. Without unrestricted legal assistance. Without unrestricted consular access. Without phone calls with family. Without evidence. This is not an open or fair process. Enough is enough,” Ross wrote on Twitter.

Whelan was detained in Russia late last year on espionage charges, an allegation he denies. His family maintains he had traveled to Russia to attend a wedding and that he was entrapped and falsely arrested.

Paul Whelan’s brother, David, told CNN on Thursday that he was not surprised when he learned that Paul’s detention had been extended for the fourth time since he was arrested last December, adding that Whelan’s lawyer has said his trial is now unlikely to happen before next spring.

“The Russian government continues to drag out Paul’s case,” David Whelan said. “Unfortunately, the Russian legal system is not concerned with justice.”

The latest development in Whelan’s case comes as his situation gathers greater attention on Capitol Hill. On Tuesday, the US House of Representatives passed a bipartisan resolution calling on the Russian government to present “credible evidence” or release him from prison. A companion resolution has been introduced in the Senate.

“Congress will not tolerate the indefinite detention of a US citizen without evidence,” Rep. Haley Stevens, a Michigan Democrat who represents Whelan’s district, said Tuesday. “We have repeatedly asked the Russian government to provide Paul with a fair and transparent judicial process to no avail.”

Whelan’s sister, Elizabeth Whelan, made a rare public appearance at a press conference in the Capitol last month, saying that Whelan has become ” trade fodder” in a geopolitical feud.

“Our family has been focused on one thing: bringing Paul home,” Elizabeth Whelan said. “We have endured a systemic lack of transparency both with respect to the Russian court proceedings as well as Paul’s conditions of confinement.”

The family continues to press US officials over Paul’s detention, but they are unsure what further action is being taken after US Ambassador to Russia Jon Huntsman retired earlier this month.

“Unless the White House acts, through the State Department, Paul will remain in Russia, and in prison, for many months and perhaps years to come,” David Whelan told CNN.

In previous court hearings, Whelan – a discharged US Marine reservist who is also a citizen of the UK, Canada and Ireland – has complained that his rights were being violated and prosecutors were acting on behalf of the Federal Security Service, Russia’s domestic intelligence service. At a court appearance back in May, Whelan said he is a political hostage, has been repeatedly threatened and is “constantly subjected to” abuse and harassment.

The case has also drawn international attention as questions persist over Whelan’s treatment and the grounds of his arrest. The US Embassy first publicly protested Whelan’s treatment in early July, and his family has said he needs more extensive medical care.

Earlier this year, Russian Deputy Foreign Minister Sergei Ryabkov told the Russian news agency RIA-Novosti that the government had ruled out the possibility of exchanging Whelan for Maria Butina, saying Whelan had yet to be sentenced in court. Butina is a Russian national currently serving an 18-month sentence in the US after pleading guilty to acting as unregistered foreign agent. She is scheduled to be released from a federal prison in Tallahassee on Friday.