Prime Minister John Howard today said he could not interfere with Schapelle Corby's drugs trial in Bali, despite her pleas for him to help her return home.

Corby, 27, who is accused of smuggling 4.1kg of marijuana into Bali on October 8 last year, has begged Mr Howard for justice, saying she is innocent.

But Mr Howard said he could not interfere in her case.

However, he said the federal government had prepared a letter for the Bali court hearing Corby's case outlining allegations of Australian airport baggage handlers trafficking drugs in passengers' luggage.

"The letter was settled on Friday by the attorney-general," Mr Howard told the Ten Network.

"But I cannot interfere in a justice system of another country.

"I cannot and would not interfere with the justice system of our own country.

"It's fundamental to our system of democracy that the executive arm of government doesn't interfere with the judiciary," he said.

"I know that if a foreigner were arrested in Australia and charged with an offence and the president or prime minister of another country started telling our courts what to do, Australia would be mightily angry.

"But having said all of that I feel for the girl, I think the whole country has been drawn into this and I can only repeat my fervent hope that the verdict is true and fair and right and just."

A Melbourne newspaper said Corby had pleaded with Mr Howard to bring her home to Australia.

"Mr Howard, as a father and as a leader, I plead for your help," the newspaper quoted her as saying.

"I did not do this. I beg for justice.

"I don't know how much longer I can do this. Please bring me home. Please."

The Denpasar District Court will hand down a verdict on May 27.