The mayor of London, Ont., who was convicted last week on three fraud-related charges from his time as a federal Liberal cabinet minister, announced Monday that he is stepping down.

Joe Fontana issued the statement days after he was convicted of fraud, forgery and breach of trust after a judge found he forged an expenses document submitted to the House of Commons in 2005 that resulted in a $1,700 government fraud.

"I am taking this step out of respect for the office of the mayor, the people of London and our judicial system," Fontana wrote in the statement Monday. "Over the next two days I will be speaking with fellow council members and city staff to ensure a smooth transition for whomever takes the interim mayor's position."

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After he was found guilty Friday, Fontana wouldn't say what the criminal convictions meant for his political future and he had previously not committed to running again in the October municipal elections.

Sentencing arguments are scheduled for July 15 and the penalties range from an absolute discharge to time in custody. According to municipal law expert John Mascarin, any term of imprisonment – even a day or intermittent weekend sentence – would disqualify Fontana under the Municipal Act from holding office.

Fontana will hold a press conference on Thursday.

When he was a Liberal member of Parliament, 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 Justice 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.

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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.