By Phil Mercer BBC News, Sydney

It was billed as the most explosive day of Australia's wheat-for-weapons inquiry.

Mr Howard has consistently denied knowledge of the alleged kickbacks

After three months of testimony, investigators finally had their chance to quiz Prime Minister John Howard about what he knew about bribes that Australia's monopoly wheat exporter had allegedly paid to Saddam Hussein.

AWB Ltd is accused of funnelling millions of dollars in kickbacks to the former Iraqi leader to win lucrative grain contracts under the UN's oil-for-food programme.

The bucks ended up with Saddam Hussein but the policy buck stops with John Howard Opposition leader Kim Beazley

But instead of fireworks and drama, the commission heard a series of flat denials from a master politician.

Sydney's Daily Telegraph said simply that the Prime Minister "blandly answered a few questions and left".

The cross-examination lasted just over 40 minutes and was far from taxing.

Carefully managed

Critics have said that is hardly surprising given that Mr Howard established the inquiry himself and carefully set out its terms of reference.

The prime minister decided what parts of the murky oil-for-food business can and cannot be judged.

There are strict no-go areas.

Exports to Iraq play a major role in Australia's wheat industry

The behaviour of the government in the wheat-for-weapons scandal is off-limits. The hearing does not have the authority to question the competence of ministers.

Its job is to determine if AWB staff broke any Australian laws in their dealings with Saddam. If they did then the inquiry can recommend that charges be brought.

Protesters tried their best to unsettle John Howard as he strolled to the court-room at a city centre office block in Sydney.

"Liar, Howard, you're a liar! Stinking liar!" shouted one irate demonstrator.

The veteran conservative was the third high-profile member of the government to testify this week, following his deputy Mark Vaile and trusted Foreign Minister Alexander Downer.

Mr Howard has always maintained he has nothing to hide.

"By appearing, by establishing the inquiry, by seeing two senior ministers appear, this government has demonstrated its transparency," he has said.

All three men insisted they did not read or receive diplomatic cables that warned that AWB might be involved in corruption. These letters dated back to 2000 and raised concerns about the company's dealings in Iraq.

Critics want to know what happened to these important pieces of intelligence - 21 documents in total - that were sent over a period of four years.

Opposition fury

The opposition believes that senior ministers must have known what was going on. If they didn't they were asleep on the job and should resign.

Either way the AWB affair is a scandal on a gigantic scale, according to leader of the Labor opposition Kim Beazley:

"This is a shocking national security failure," he fumed. "The bucks ended up with Saddam Hussein but the policy buck stops with John Howard."

The government, which sent troops to join the US-led invasion of Iraq, has said the first it knew of the corruption allegations surrounding AWB was in October last year.

June deadline

A UN report stated that the Australian exporter, along with dozens of other companies, had paid bribes to Iraq under the oil-for-food scheme.

The programme ran from 1996 to 2003 and allowed Baghdad to sell oil to raise funds to buy food and medicine to help civilians hit by sanctions against Saddam Hussein. AWB was the largest single supplier of humanitarian goods.

The Sydney inquiry headed by retired judge Terence Cole is due to hand down its findings by the end of June.

As it stands, the Howard administration should avoid any major damage. There would need to be some spectacular, and unexpected, evidence in the commission's final weeks for it to take a real hit.

Opinion polls suggest that most Australians are more worried about rising fuel costs than allegations of bribery in a distant country.

"Clearly, the Howard government sees the Cole inquiry as being about as politically dangerous as the revelation that John Howard wears odd socks," wrote Greg Craven from Curtin University in The Australian Financial Review newspaper.