Senator Mike Duffy has been exploring the possibility of legal action against the federal government since his exoneration on 31 criminal charges, fuelling rumours in Ottawa about an impending showdown, sources said.

"Senator Duffy has made no decisions on this matter," Andrea Guzzo Lehman, Mr. Duffy's parliamentary affairs and communications adviser, said in an e-mail to The Globe and Mail.

Mr. Duffy is said to have retained Ottawa lawyer Lawrence Greenspon, who writes on his website that he "represents the little guy against governments, institutions, insurance companies and corporations."

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Read more: The Mike Duffy dossier: What you missed in his courtroom drama

When asked if Mr. Duffy is preparing legal action against the government, Mr. Greenspon wrote in an e-mail, "Thank you for your interest but there is nothing that I wish to talk about at this time."

It is not known which legal avenue, if any, the senator would take. His trial lawyer, Donald Bayne, has publicly stated that Mr. Duffy should be repaid the approximately $270,000 in wages he lost while under Senate suspension for almost two years. Mr. Bayne, who said he would not be representing Mr. Duffy in any future civil suit, has also previously said the senator could pursue a lawsuit against the government.

Speaking to The Globe after the verdict in Mr. Duffy's trial in April, 2016, Mr. Greenspon, who specializes in both criminal and civil litigation, also said Mr. Duffy should be repaid his wages because "to do otherwise is completely to violate the presumption of innocence."

He said Mr. Duffy could pursue civil avenues against the government on the grounds of a conspiracy to interfere with his livelihood or damage his reputation.

Reached by e-mail on Wednesday, Mr. Duffy did not provide further information on the timing of any possible court action against the government.

Senators have also been hearing rumours that he is preparing to sue. A Twitter account called @MikeduffyMike sent out its first tweet in more than a year Wednesday – "Test Post from Mike Duffy" – linking to the website mikeduffy.ca.

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Mr. Duffy was charged by the RCMP in July, 2014, with fraud, breach of trust and bribery in relation to his Senate expense claims and consulting contracts and for accepting $90,000 from Nigel Wright, then-chief of staff for prime minister Stephen Harper, to repay the expenses.

Prior to being charged, Mr. Duffy, along with senators Pamela Wallin and Patrick Brazeau, was kicked out of the Conservative caucus and suspended without pay from the Senate by his colleagues in November, 2013, for submitting what were considered questionable housing and travel expenses. Mr. Duffy's salary kicked in again when the election was called in August, 2015.

He returned to the Senate in May, 2016, as an independent. After being under RCMP investigation for three years, Ms. Wallin was never charged. After Mr. Duffy's trial, fraud and breach of trust charges against Mr. Brazeau were dropped, as were charges against retired Liberal senator Mac Harb.

Fellow senators could have put forward a motion to reimburse their colleagues for lost wages, but no one did.

In April, 2016, Ontario Court Justice Charles Vaillancourt acquitted Mr. Duffy on all 31 charges, delivering a verdict that strongly criticized the actions of the Prime Minister's Office, which the judge described as "mind-boggling and shocking." He issued a 308-page decision in which he called Mr. Duffy a "credible witness" whose conduct was "reasonable and honest." He dismissed every charge related to the senator's residency, travel claims, contracts and a $90,172 cheque from Mr. Wright.

It was the actions of Mr. Wright and other top Harper lieutenants, in pushing Mr. Duffy to pretend he had repaid questionable expenses out of his own pocket, that drew the judge's harshest criticism.

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"I find based on all of the evidence that Senator Duffy was forced into accepting Nigel Wright's funds so that the government could rid itself of an embarrassing political fiasco that just was not going away," Justice Vaillancourt said.

At every step of the political drama, Mr. Duffy had resisted "threats and pressures" from the PMO and the Conservative Senate leadership and was "dragged kicking and screaming" to repay living expenses he believed he was legally entitled to collect, the judge found.