International co-prosecutor Andrew Cayley yesterday announced his resignation from the Khmer Rouge tribunal, departing just weeks before the court is set to hear closing arguments in the first phase of the case against the regime’s two highest-ranking living leaders.

In a brief statement circulated by the Extraordinary Chambers in the Courts of Cambodia yesterday, Cayley announced that his departure was for “personal reasons” and called for a resolution to the funding issues that have seen hundreds of national staff at the hybrid court go for months without pay.

In an interview, Cayley stressed that his departure had nothing to do with the ongoing struggles of the court and said he would be “moving to other legal work”, though he declined to give details on his next appointment.

“It really has been a very great pleasure to work with this court. We faced immense challenges, but I think a lot of good has come out of it, and I think ultimately, for all of the criticism and the cynics, there will be a measure of justice at the end of all this,” he said.

“I don’t think the court is failing.”

Announcement of Cayley’s resignation, which was sent to the UN last month, comes as the court struggles with a financial crisis that has slowed work to a standstill in some departments. More than 140 national staff have been on strike since the beginning of September over months of unpaid wages.

In a statement issued last week, Human Rights Watch accused the government of shirking its duty to cover Cambodian salaries in order to obstruct the court’s work. The same day, the UN’s special expert to the tribunal, David Scheffer, called the budget crisis wholly the blame of the government, which is legally obliged to find funding for the national side.

Cayley yesterday said he believed the government and UN were on track in securing finances for the cash-strapped national side but said national employees had been “suffering” in the meantime.

“Some of them have children, some of them are the only person working in the family and they work very hard. In the [office of the co-prosecutors], genuinely we have an extremely good relationship with the nationals. [Working] without them [would be] extremely problematic,” he said.

Court spokesman Neth Pheaktra said as of yesterday no solution had been broached and that staffers had grown “very concerned about the function of this court.”

Cayley arrived in late 2009, shortly after the departure of Robert Petit, who left the court after three years for personal reasons. While Petit was an at-times outspoken critic of government interference at the court, Cayley has been more circumspect over the years. But his job has, at times, brought him into direct conflict with top judges.

In 2011, when the co-investigating judges tried to quietly shut down investigations into the government-opposed Case 003, Cayley released a rare public statement accusing the judges of failing to thoroughly examine the case. In response, he was publicly censured and threatened with contempt-of-court proceedings.

He is set to be replaced by the reserve international co-prosecutor Nicholas Koumjian, who is expected to arrive next month, Cayley said. A senior war crimes lawyer, Koumjian has spent more than a decade at, variously, the Special Court for Sierra Leone, the International Criminal Court, the Serious Crimes Unit in East Timor and the International Criminal Tribunal for the Former Yugoslavia.

Koumjian could not immediately be reached for comment. However, in a video interview given last year with Armenian news channel CivilNetTV, he defended the international judicial system.

“For those who were victimised, for those who suffered, there is not a feeling of justice until there is justice. It’s very important that those most responsible be brought to justice,” he said.

Though the timing of Cayley’s departure is unfortunate, potential problems could be mitigated if the UN “takes pains to make sure the replacement is a strong and courageous prosecutor”, Open Society Justice Initiative tribunal monitor Heather Ryan said.

“If they can get a prosecutor on board quickly, it will be the key to seeing motion on future cases. That will do a lot to mitigate the perception that the court doesn’t have a strong prosecutor on board.”

Cayley said he had taken pains to ensure measures were in place for a smooth transition. “[Deputy co-prosecutor] Bill Smith and [national co-prosecutor] Chea Leang will do the closing oral submissions,” he said, adding that his plan had originally been to stay until the completion of arguments.

In interviews given at the time of his arrival, Cayley was adamant that he expected to stay until the “completion of the mandate of the court”.

“I did think, when I came, that the court’s mandate would actually be finished by now,” he said yesterday. “It hasn’t and personal and family circumstances now dictate that I’m going. I don’t think anybody believed that we’d be here at this stage we are.”