Nadine Dorries MP has vowed to "go after" Ipsa after the parliamentary watchdog revealed it was investigating her expenses.
She insisted she was "totally relaxed" about the allegations, saying they were completely unfounded.
One relates to a travel ticket claim that was submitted twice in error by a member of staff who had accidentally "pressed the button twice", she said.
"Ipsa was asleep on the bloody job not filtering out claims like that," she added.
Ms Dorries said Ipsa was also accusing her of subletting her flat because it was used by her daughter over three months while she was was home from university.
"I have never misclaimed one penny on my expenses," she said.