A former close friend of Roxy Jacenko's husband says he has a 'gambling problem'.

Investment banker and husband of PR mogul Roxy Jacenko, Oliver Curtis, has been accused of having a gambling problem in his insider trading trial on Wednesday.

Curtis is charged with conspiring with former best friend John Hartman to commit insider trading offences that procured the friends an alleged $1.4 million between May 2007 and June 2008.

Senior Crown Prosecutor David Staehli SC told the court on Monday the former friends used the profits to pay $156,420 for 12 months’ rent in advance on a luxury Bondi apartment as well as a group holiday to Canada and Las Vegas, The Daily Telegraph reports.

It was also alleged that Curtis withdrew money so Hartman could buy a Mini Cooper and a Ducati motorcycle for $80,000.

The Daily Mail reports the court heard that a series of emails exchanged between the pair may have revealed the lavish extent of their lifestyle.

Hartman was questioned about the exchanges and said that he and Curtis looked at cars, motorbikes and a plasma television for their $3,000 a week Bondi apartment.

Hartman told the court that he and Curtis paid for a group holiday using some of the money from the scheme.

He said the friends invited on the trip had no idea where the money had come from.

One trip that was raised was a holiday to Canada and the United States where Curtis is alleged to have paid for their friends to travel between ski resort Whistler and Vancouver in a helicopter.

The Daily Mail reported that emails sent by Curtis to Hartman and several other men explained their travel arrangements.

Celebrating @bebejdavis birthday. We have not given her anymore spray tan vouchers this year - it appears she used the last ten in one go!!!!!! Hip hip hooray !!

A photo posted by Roxy Jacenko (@roxyjacenko) on Apr 22, 2016 at 8:38pm PDT

It is alleged that in regards to the helicopter, Curtis said: "We will all be very hungover and not enjoy a 2-hour drive."

Curtis also allegedly said he'd "spread the love" by shouting the group's flights between Canada and the United States at a cost of $3,600.

The friends were reported to have stayed in five-star hotels and been chauffeured around Las Vegas in Rolls Royces.

"I think we both did, sir," he said.

Hartman also agreed when Thangaraj suggested the pair were betting "hundreds and thousands of dollars" in total.

Hartman went on to specify that large amounts may have been spent on singular occasions.

"Might have been one or two occasions where there were tens of thousands, maybe $10,000," Hartman said.

The court heard Hartman and Curtis agreed to evenly split the money allegedly raised.

The pair were best friends from childhood after both attending St Ignatius College Riverview.

The trial is ongoing.