TORONTO - Former Conservative MP Dean Del Mastro lost his appeal of his election overspending case and was taken away to jail Tuesday, after an Ontario judge found he had committed offences that "strike at the heart" of the democratic process.

Del Mastro was convicted in the fall of 2014 for violating the Canada Elections Act during the 2008 election and was sentenced last summer to a month in jail.

He was granted bail after a night behind bars as he launched an appeal, with his lawyer arguing for no time in jail while Crown prosecutors pushed for a longer incarceration period.

Justice Bryan Shaughnessy, who heard Del Mastro's appeal in Oshawa, Ont., found that the judge at the disgraced politician's original trial made no significant errors in her findings.

"The appeal as against conviction is dismissed," he said in court. "The appeal as to sentence is dismissed. Dean Del Mastro shall be taken into custody, immediately, to serve the balance of his sentence."

Del Mastro's lawyer, Leo Adler, said he was disappointed with Shaughnessy's decision and would be "reviewing all options."

Del Mastro - former prime minister Stephen Harper's one-time point man on defending the Tories against allegations of electoral fraud - was convicted of three electoral offences: overspending, failing to report a personal contribution of $21,000 he made to his own campaign, and filing a false report.

He resigned from his Peterborough, Ont., seat in the House of Commons - where he had been sitting as an Independent since being charged - shortly after he was found guilty, although he maintained his innocence throughout his legal saga.

Shaughnessy, however, found that Del Mastro's offences were grave ones.

"Violations of the election spending limits and deliberate and concerted efforts to evade compliance with the honest and truthful reporting of contributions and expenses, such as occurred in this case, is a serious affront to our democratic system of government and fairness of our election process," he said.

"The offences that Dean Del Mastro committed ... are serious and do strike at the heart of our democratic electoral process."

Much of Del Mastro's case pitted his own testimony against that of the president of a now-defunct data consulting firm called Holinshed, whose services lay at the centre of the trial.

Del Mastro's defence took the position that Holinshed's president, Frank Hall, was lying to the court about the nature of the work he had done for Del Mastro during the 2008 campaign period.

During the trial, Del Mastro denied Hall's claim that Holinshed provided hundreds of hours of voter-ID calling for his 2008 campaign - a claim that was supported by emails between Hall and Del Mastro that were found on Hall's computer by investigators.

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Del Mastro testified that he had rebuffed Hall's efforts to get him to buy Holinshed's voter ID services, and denied ever receiving or sending the emails in question.

The trial judge accepted Hall's evidence that his firm was working for Del Mastro during the election period and found there had been no evidence of tampering with electronic data.

She concluded at trial that Del Mastro had lied and cheated and his conduct had been an affront to democracy.