Perth: The navy's maritime command knew of reports suggesting an overloaded boat had left Indonesia for Australia on October 20 last year but took no action, a senior naval commander said.

Maritime Commander Rear Admiral Raydon Gates, who prepared a report on Australia's knowledge of the boat which sank killing 353 people, has been prevented from giving evidence about it to a Senate inquiry into the children overboard controversy.

Defence Minister Robert Hill had eight times rejected requests for him to appear.

Speaking publicly for the first time about the issue today, Rear Admiral Gates said the boat known as SIEV X, was one of nine boats the navy was tracking at the time and information about it was scanty.

"It was certainly not enough in my opinion as an operational commander to start to move assets to that affect," he said.

"We were still unconvinced, from my reading of it, that the thing had sailed anyhow."

He said there was a constant flow of information between defence's joint intelligence unit and maritime command.

"It (maritime command) knew about SIEV X as one of many and with sketchy information," he said.

Rear Admiral Gates said that under the circumstances the navy was justified in not actively searching for the vessel.

"Let me stress to you it wasn't an oversight by the navy," he said.