Political leaders called on former chief executive Donald Tsang Yam-kuen yesterday to give a full account of his alleged attempt to secure a private audience with the pope in 2008.
Sources said the administration would look into the claims, but said the government was confident Hong Kong's judicial integrity was not compromised.
The South China Morning Post yesterday reported allegations made by former Italian senator Sergio De Gregorio.
He claimed to have tried to broker a deal between Tsang's administration and the scandal-plagued former Italian prime minister Silvio Berlusconi.
The Italians agreed to help Tsang secure a private audience with Pope Benedict XVI.
But in return, the Hong Kong side was allegedly asked to stop the transfer of evidence seized in the city to Italian prosecutors probing a fraud and money laundering case linked to Berlusconi.
Archbishop Eugene Nugent, then the Catholic Church's representative in Hong Kong, told the Post yesterday that Tsang made at least three requests to meet Pope Benedict XVI . Political leaders yesterday said this would have violated diplomatic protocol laid down in Article 13 of the Basic Law.
The protocol clearly states that military and foreign affairs must be handled through the central government.
Tam Yiu-chung, chairman of the Democratic Alliance for the Betterment and Progress of Hong Kong, believed Tsang had acted "inappropriately".
The Beijing-friendly lawmaker said: "It was not appropriate for Tsang to seek a meeting with the pope regardless - after all he is the leader of Hong Kong, not any ordinary citizen. He should have sought approval from Beijing [first]."
He said it would not have been possible for Tsang to meet the pope "in a private capacity", as being the city's chief executive is a 24-hour-a-day duty. Others questioned whether Tsang abused his position by using public resources to obtain a personal favour.
De Gregorio claimed Tsang sent senior Hong Kong officials to Rome to discuss the matter.
Tsang denied the claim. But Duncan Pescod, the city's representative to the European Union at the time, confirmed he went to Rome to discuss with an Italian senator the possibility of arranging a private meeting between Tsang and the pope.
Civic Party legislator Ronny Tong Ka-wah said Tsang would have abused public resources if the claims were found to be true.
"It is unacceptable for Tsang to use public officials to serve a private purpose of meeting the pope," said Tong, who is a senior counsel.
But he said further evidence was needed to draw a conclusion.
Tsang told the Post on Thursday through his press officer that he had "never written through Mr Pescod to Pope Benedict and requested an audience".
But Pescod, now the housing chief, said: "The Brussels Economic and Trade Office was involved in an attempt to arrange an audience for the former CE [Tsang] and the former pope [Benedict XVI]."