A former Conservative MP's constituency office manager was subjected to "constant bullying", an ex-treasurer of the local party has told a tribunal.
Mark Rhydderch-Roberts spoke in support of Sarah Lewis, who is suing Chris Davies for constructive dismissal.
She said there was a "climate of fear" as Mr Davies turned against her after she uncovered £700 of false invoices.
Mr Davies later admitted making false expense claims and lost his seat as MP for Brecon and Radnorshire.
Ms Lewis told the employment tribunal in Cardiff she noticed discrepancies with invoices for photography work in 2016.
"I made the decision not to submit the invoice to the Independent Parliamentary Standards Authority (IPSA) as I knew it was a false invoice," she said.
After that Ms Lewis said Mr Davies's attitude towards her became "substantially more critical and negative" and he "distanced" himself from her.
The tribunal also heard about an earlier incident where errors in submitting expenses meant Mr Davies had to pay back £4,000 to IPSA.
Ms Lewis described how he banged on the filing cabinet in her office and said: "I thought the whole point of becoming an MP was to get rich".
She said she did not know if this was a joke or not.
When challenged about this incident by Mr Davies's solicitor Irvine McCabe, Ms Lewis said: "I've sworn to tell the truth - and I'm telling the truth."
Mr McCabe then referred to a meeting the then-MP called in November 2017 to discuss the way Ms Lewis was doing her job, saying he had "perfectly legitimate" reasons to speak to her.
"He knew you'd received money to which you were not entitled... and he had evidence that you weren't in the office when you should have been," the solicitor said.
Ms Lewis explained she had been overpaid after her working hours were cut because Mr Davies had not submitted her amended hours by the monthly deadline.
She also claimed that messages and emails had gone unanswered as she had taken a two-week holiday and no-one had been brought in to cover for her.
"He was belittling the work I do," she said.
Mr Rhydderch-Roberts, who was constituency treasurer at the time, told the tribunal he was aware of constant bullying and intimidatory tactics against Ms Lewis.
After hearing about the November meeting, he said he emailed Mr Davies to say: "I have just had a distraught Sarah Lewis on the phone following what appears to be a very ill-natured and unnecessary conversation.
"Just to be clear, Sarah has been a tremendous asset to the association and behaves with impeccable integrity in everything she does."
The tribunal heard there were already tensions between local officers and their MP, with the treasurer saying in an email to Ms Lewis in August 2017 that it would be "a blessed relief to be free of any further interaction with Chris and his motley kitchen cabinet", referring to them as "cheats" and "liars".
Ms Lewis went on sick leave in January 2018 and quit her job at the constituency office in Brecon a few months later.
Following an investigation, Mr Davies was charged in connection with false expenses claims in February this year, and was fined in April after pleading guilty.
He was unseated as MP for Brecon and Radnorshire following a recall petition by constituents and lost to the Liberal Democrats after seeking to win the seat back at a subsequent by-election.
The tribunal will resume on Wednesday.