Tory MP Christopher Davies has been fined £1,500 and ordered to carry out 50 hours of community service for submitting false expenses invoices.
He was told he had committed “two very serious offences” which were “absolutely intended to deceive” when he appeared before magistrates last month.
Sentencing the Brecon and Radnorshire MP on Tuesday, Mr Justice Edis said: “It seems shocking that when confronted with a simple accounting problem, you thought to forge documents.
“That is an extraordinary thing for a man with your position and your background to do.”
Mr Davies showed no emotion when his sentence was read out at Southwark Crown Court in central London.
The two charges related to the period when Davies was setting up his constituency office following the 2015 general election.
He had contacted a photographer and bought nine images from them to decorate and display in his constituency office, using his own money to pay the £700 for them initially.
There were two budgets available to him, the Start Up Costs Budget – for office furniture and IT equipment – and the Office Costs Budget, both of which he could claim the full amount from.
But Philip Stott, prosecuting, revealed Davies found in February 2016 that only £476.02 was left in the Start Up Costs Budget, with £8,303.75 remaining in the other.
He then created two fake invoices, so the £700 cost could be split between the two budgets – £450 to the Start Up and £250 for the other.
Defending, Thomas Forster QC said his client – a 51-year-old father of two school-age children – was in a “privileged position” as an MP, but that his offending was a mistake rather than a “return to the bad old days” of “maxing out expenses accounts”.
He said: “There is a very real likelihood that his political career is in tatters.”
Prosecuting, Mr Stott said it was accepted that Davies had not sought to profit financially from the action and that he was entitled to claim for the pictures.
But he added the 51-year-old was not entitled to split the costs across two budgets, and said any claims had to be accompanied by genuine invoices.
Davies served as parliamentary private secretary to the Wales Office from January to July 2018.
Under parliamentary rules, he does not automatically lose his seat as an MP because his sentence was less than the 12-month minimum.