Former Prime Minister Ehud Olmert's attorneys said on Monday that any irregularities in travel reimbursements in the so-called Rishon Tours affair stemmed from disorder, not fraud.

Prosecutors charge that Olmert billed more than one organization for official trips via the Rishon Tours travel agency and used the proceeds. Olmert is on trial with his bureau chief, Shula Zaken.

"The picture that arises in this trial is completely unlike a conspiratorial situation of systematic fraud," said Olmert lawyer Navit Negev on the first day of defense arguments at the Jerusalem District Court.

"The prosecutors have drawn an extreme portrait, but gradually new pieces in the mosaic are emerging and creating a much more realistic picture - one much more compatible with human character."

The defense notes that the indictment covers 15 trips in a period when there were 71 relevant journeys.

"The fact that there were trips [unconnected to the fraud charges] contradicts this image of systematic fraud," the defense said. "It conforms with an image of disorder, and nothing connected to systematic behavior."

Olmert contends that Rishon Tours did not operate in an orderly manner. "It acted on its own initiative and did not always update Olmert and his staff about its actions," Negev said.

The defense will give further testimony on Tuesday and Wednesday. It is expected to finish pleading its case by the end of the month.