Former parliamentary Speaker Peter Slipper has been found guilty of dishonestly using taxpayer-funded travel vouchers.

Mr Slipper had admitted using commonwealth Cabcharge taxi vouchers to pay for trips to wineries outside Canberra in January 2010.

But the former MP denied he acted dishonestly.

The ACT Chief Magistrate Lorraine Walker thought otherwise after a week-long hearing, finding Mr Slipper guilty on Monday of three counts of dishonesty.

An impassive Mr Slipper sipped from a glass of water as the verdict was delivered.

He will be sentenced on September 22.

Mr Slipper’s lawyers indicated more evidence might be presented to the court prior to sentencing.

The court had been told Mr Slipper’s life had spiralled into despair as a result of the dishonesty charges, and in 2013 he had twice attempted to take his own life.

In June, his lawyers argued unsuccessfully for the charges to be dismissed under the Mental Health Act due to his state of mind.

On three winery trips Slipper used multiple Cabcharge vouchers to divide the $900 in fares into smaller amounts, using descriptions like “parliament to suburbs” and “suburbs to suburbs”.

The prosecution alleged Slipper knew that he was breaking the rules covering travel entitlements of parliamentarians and that his actions could cause a financial loss to the commonwealth.

Ms Walker, in handing down her decision, said it wasn’t unusual for Slipper to fill out multiple cab charges by hand instead of paying electronically.

“The issue is what he put in those vouchers,” she said.

The suggestion Slipper was visiting suburbs was “implausible” when his real destination was wineries well outside Canberra.

“The contents of these vouchers is clearly false,” Ms Walker said.

She was satisfied Slipper was dishonest, and there was only one reason he would fill out the Cabcharges incorrectly.

“That was to misrepresent what he was actually doing.”