'No moral equivalence' over Russia prisoner swap talk

There should be no moral equivalence drawn from any prisoner swap for an Australian fighter being held in Russia, a former ambassador says.

A prisoner of war swap has become more complicated after Russia sentenced Australian Oscar Jenkins to 13 years in a maximum security prison on criminal charges for fighting with the Ukrainian military as a mercenary.

Foreign Minister Penny Wong branded it a "sham trial", saying Mr Jenkins should be classified as a prisoner of war, which comes with added protections under international law.

Australia's former ambassador to Russia Peter Tesch said the sentencing showed the Kremlin was engaging in hostage diplomacy, which is when trumped-up criminal charges are leveraged to get back Russian prisoners.

"This could put him outside prisoner swaps with Ukraine and at another level. It could be Russia starting to look at who they want in other prisons," Mr Tesch told AAP.

High-profile cases include Russia swapping American journalist Evan Gershkovich and former US Marine Paul Whelan for 24 detainees across western nations.

"They had very obviously done that with a view to use them as assets in an eventual negotiated exchange," Mr Tesch said.

Ukraine is handling the negotiations with Russia, with past prisoner of war swaps occurring between the two nations.

But there is internal doubt over whether Russia would include Mr Jenkins in a similar deal given the added leverage of him being Australian.

This was underscored by Russia sentencing him through criminal charges rather than holding him as a prisoner of war.

The former envoy wouldn't speculate on potential swaps or what should be done to get Mr Jenkins back.

But he was keen to make the point there was "a false equivalence when we talk about prisoner swaps because we don't take people political hostage".

"Any of the names that have been swirling around, like the Korolevs, they are Australian citizens who have been subject to due process with rights of appeal based on criminal charges," Mr Tesch said.

"To talk about a prisoner swap applies legal and moral equivalence and that just doesn't apply in this case."

Married couple Kira Korolev and Igor Korolev have been charged with espionage and face 15 years behind bars.

They are yet to enter pleas, but the Kremlin has criticised the charges, saying the arrests were an attempt to trump up "another wave of anti-Russian paranoia in Australia".

This was denied by the Australian government.