He says it would be “undesirable, inappropriate and unsatisfactory” for the senate committee to ask him questions about matters dealt with in his report.
In a letter obtained by Sky News, Mr Heydon reveals his attendance was requested by the committee five days after it was reported in the media.
The former High Court justice was listed as a witness for a public hearing for the senate education and employment committee’s inquiry into legislation to crack down on union corruption on October 4.
Media reported the listing on September 22.
But Mr Heydon says he did not learn of the plan until September 27, when an email to his clerk “tentatively” enquired about his availability.
He has written to committee chair Nationals senator Bridget McKenzie to advise he does not want to attend.
He says there is no point for a commissioner to comment on their own report, particularly on adverse recommendations made about certain people involved.
“It is undesirable, inappropriate and unsatisfactory that questions should be asked of an ex-royal commissioner about matters dealt with in the royal commission reports,” he wrote.
Mr Heydon referred several union members to authorities.
It would be inappropriate, he said, to repeat in public the adverse findings against certain figures when “they may fear that the repetition of the material may have an adverse effect on any future criminal or civil proceedings”.
In addition, Mr Heydon said his opinions on the bills were contained in the trade union royal commission reports that were released last year.
“It would be a waste of time for my views to be stated orally to the committee when they have been stated in great detail in those reports,’ he said.
Mr Heydon’s appearance at the committee could have presented Labor senators with an opportunity to grill the former justice over alleged bias.
The ex-royal commissioner came under fire last year for accepting an invitation to speak at a Liberal Party fundraiser, prompting union calls for his sacking.
Unions said at the time his acceptance, and later withdrawal, of the invitation created at least the perception of bias, while Labor said his job was untenable.
Mr Heydon ruled himself fit to continue as royal commissioner, but the issue was a distraction for the coalition, which wanted to focus on “union thuggery”.
The government is trying to push through twice-rejected legislation to resurrect the Australian Building and Construction Commission after it was used to trigger a double-dissolution election.