Following the reports by several news outlets, Attorney General Christian Porter said on Tuesday he had referred the allegations to an anti-corruption body that investigates federal agencies, since they related to government officials.

After days of issuing brief statements denying wrongdoing, Crown circulated a letter signed by its board late on Wednesday, accusing the papers of waging a "deceitful campaign" that had unfairly attempted to damage its reputation.

"Much of this unbalanced and sensationalised reporting is based on unsubstantiated allegations, exaggerations, unsupported connections and outright falsehoods," the directors said in the letter.

Signatories included Crown Executive Chairman John Alexander, former finance department head Jane Halton, former communications minister Helen Coonan and Geoff Dixon, the former chief executive of Qantas Airways.

That statement appeared as full-page advertisements in papers owned by News Corp on Thursday. However, the Sydney Morning Herald and the Age newspapers, which published the articles, said they had refused to run the advertisements and instead carried a line-by-line response to Crown's statement.

"The stories were carefully sourced using Crown's internal documents, former employees, credible commentators, dozens of sources from the industry, law enforcement and elsewhere, and careful verification," the newspapers wrote in response to the Crown's letter.

The papers, owned by Nine Entertainment Co Holdings, added that they had asked Crown for an interview and sent 63 questions days before the reports, to which Crown responded "with a short statement" declining to comment on individuals.

Crown shares have fallen 6.4% in three trading days since the papers, and Nine's "60 Minutes" television news programme started running the reports.

(Reporting by Byron Kaye in SYDNEY and Nikhil Kurian Nainan in BENGALURU; Editing by Sam Holmes)

By Byron Kaye