Federal minister Anthony Albanese says the opposition may have breached the Crimes Act by calling for MP Craig Thomson's resignation.
Mr Thomson faces civil court action by Fair Work Australia over his alleged misuse of Health Services Union member funds when he was national secretary from 2002 to 2007.
Opposition Leader Tony Abbott said on Friday: "The best thing for everyone - to take the pressure off him, to take the pressure off his family - would be for (Mr Thomson) to leave the parliament."
Mr Albanese said Mr Abbott had gone a step too far.
"They've now gone the next step," Mr Albanese told ABC radio.
"They've now gone to the step which is a breach of Section 28 of the Crimes Act in attempting to suggest that `we'll lay off if you just resign from parliament'.
"That is a very serious thing for the leader of the opposition to do."
Under Section 28 of the Crimes Act it is an offence for anyone "who, by violence or by threats or intimidation of any kind, hinders or interferes with the free exercise or performance, by any other person, of any political right or duty".
Mr Albanese said it "may well be looked at by the appropriate authorities".
"The Crimes Act is very clear about not allowing any intimidation of any kind which hinders or interferes with the free exercise of any political right or duty," Mr Albanese said.
Mr Albanese said Mr Thomson had never expressed to him any indication he would resign from parliament.
"He ... declares his innocence of all the allegations that have been made against him," the minister said.