Christine Grahame, convener of the Justice Committee, was filmed by the ex-staffer as he tried to gather evidence of alleged improper use of parliamentary resources.
A leaked email also shows her calling a Green MSP a “prissy p****” and defending a former MSP who implied a rape victim may have been a prostitute.
Grahame, 67, has been an MSP since 1999 and represents Midlothian South, Tweeddale and Lauderdale for the Nationalists.
She is embroiled in a dispute with former employee Mark Hirst, who worked for her from 2004.
Hirst, who was suspended by Grahame and dismissed last month for gross misconduct, has made allegations about the MSP to the Electoral Commission, Parliament’s Standards Commissioner, and the police.
The ex-employee claims to have evidence of staff working on SNP business and Grahame’s recent election campaign while they were being paid from the public purse.
He also alleges these staff costs were not included in her Holyrood election return.
Over a number of months, while working on her staff, Hirst gathered emails and secretly recorded his former boss in her Holyrood office.
Much of the footage has been handed to the authorities.
In addition, Grahame has been criticised over an email to former Glasgow Tory MSP Bill Aitken.
In the last Parliament, Aitken filled the role Grahame currently occupies, convener of the Justice Committee. However, he quit the post in February after suggesting to the Sunday Herald that an area in Glasgow in which a woman was raped was frequented by “a lot of hookers”.
The comments provoked outrage and led to Green Party MSP Patrick Harvie condemning the Tory politician in a parliamentary motion.
In her email, entitled “resignation”, Grahame said: “Just heard that tonight on radio. Firstly, I think the journo was a s****. Patrick is a prissy p****. Speak to you tomorrow?”
Grahame, considered a maverick by some colleagues, is overseeing the scrutiny of the Scottish Government’s anti-sectarianism Bill.
Hirst said: “I and my union believe we have a very strong case that we expect to bring against Ms Grahame in due course at an employment tribunal.
“I believe I was unfairly dismissed on grounds of gathering information with a view to whistleblowing her questionable party political and election activity at Parliament and in her constituency office.”
Harvie said: “I am sure in her calmer moments she would recognise Bill Aitken’s comments were completely unacceptable.”
A Labour spokesman said: “As convener of the Justice Committee her comments regarding Bill Aitken suggests that as Justice Committee convener she is now compromised and her judgment deeply flawed.”
A spokesman for Grahame said: “Mr Hirst is an ex-employee of Ms Grahame and was dismissed on the grounds of gross misconduct. Ms Grahame will not comment on any clandestine recordings in her private office or stolen emails.”