MP Jared O'Mara has called a former employee "ableist" after she accused him of using ill health to avoid dealing with issues.
An employment tribunal heard Margaret Flude claim the Sheffield Hallam MP used illness as an "easy excuse".
He said his mental health suffered when his staff left in April and he had to close his office for a month.
Mr O'Mara said his autism, cerebral palsy and mental health problems meant he could do some things but not others.
Mrs Flude and two other former staff members, Dawn Coop and Kevin Gregory-Coyne, have taken legal action against Mr O'Mara amid claims over holiday entitlements.
Mr Gregory-Coyne and Mrs Flude also allege breach of contract - but no details of the allegations were given.
Appearing by video link, Mrs Flude said: "Is it not true that every time there's a situation that you do not wish to do deal with you fall back on claims of ill health?"
Mr O'Mara replied: "That's ableist and it's disgusting."
She asked him why he was not able to fill in the relevant tribunal forms but still do a range of other MP activities, including travel to Westminster on 19 and 22 October for key Commons votes.
The independent MP said he attended, despite having a doctor's note, because they were "important votes".
He said filling in forms was a particular problem for him.
Discussing his mental health, the MP added: "It's been a gradual process, going downhill."
His barrister, Naomi Owen, told the tribunal: "This is someone who is really not very well at all. He has felt pursued by the press recently."
She indicated the MP would not be standing at the upcoming general election.
The hearing was also told Mr O'Mara was "destitute and penniless".
The preliminary hearing will decide whether the MP should be given more time to respond to the allegations against him.
Employment Judge Robert Little agreed to a retrospective time extension for Mr O'Mara to prepare his response.