He was found guilty last week of fraud, forgery and breach of trust after a judge ruled he forged an expense document submitted to the House of Commons in 2005 that resulted in a $1,700 government fraud.
Following the convictions, he was tight-lipped about what they meant for his political future — he had not yet announced whether he would seek another mayoral term in municipal elections in October — but days later announced he would step down.
In a statement issued Monday, Fontana announced he would resign and would hold a news conference Thursday, but he cancelled that appearance via another statement Thursday morning.
Fontana's official resignation was delivered to the city clerk and he will now focus on his family, the statement indicated.
"They have sacrificed for me for 32 years," Fontana wrote. "I will not return to public life."
This was not how Fontana envisioned his final days in office, but he accepts the challenges before him, he added.
"I understand I am required to walk this path alone and I have learned that we will be measured not only by what we do but by how we choose to carry our burdens."
Fontana's political life spanned more than 30 years, first as a municipal politician, then as a Liberal member of Parliament, ultimately returning to London as mayor.
He was born in Italy but his family moved a few years later to Timmins, Ont., where Fontana grew up, as he described to the police officer conducting his interview in the fraud investigation.
Fontana left Timmins to study chemical engineering at the University of Waterloo, but he only spent a year at the school. He and about six friends travelled as musicians — Fontana is a drummer — for about a year, then he went to the University of Western Ontario, Fontana told the officer.
After graduating he stayed in London, working for Firestone, then London Life, and in 1978 he started an insurance business and was elected as a municipal councillor.
Fontana was elected in 1988 as a Liberal member of Parliament and served as minister of housing and labour from 2004 to 2006. He left federal politics for an unsuccessful bid to become London mayor in 2006, but won the job in the 2010 election.
Sentencing arguments in his criminal case are scheduled for July 15 and the penalties range from an absolute discharge to time in custody.
When he was a Liberal MP, Fontana forged a contract from his son's wedding to make it look as though it was for a political event at the same venue, Superior Court Judge Bruce Thomas found last week.
Fontana admitted making seven changes — including whiting out his wife's signature, replacing it with his own and writing the word original in quotation marks at the top — to an existing contract with the Marconi Club for his son's 2005 wedding to reflect an event he planned for then-finance minister Ralph Goodale at the same venue.
The Goodale event didn't end up going ahead at the Marconi Club, but Fontana testified he believed the club was owed a $1,700 deposit from his MP budget, despite the club not asking for any money.
Since he had only spoken with the club's president — a friend of more than 40 years — over the phone and didn't have any paperwork, Fontana changed several details on the wedding contract from a few months prior and submitted it, he testified. The club received the $1,700 government of Canada cheque and credited it to Fontana's son's wedding.
The judge said he did not believe Fontana's story, saying the evidence pointed to the cheque being mistakenly sent to the venue. Fontana intended for it to go directly to him, Thomas found. If the money had indeed gone to Fontana, no one would have been the wiser, the judge said.
Also on HuffPost