Prime Minister Stephen Harper and Justice Minister Peter MacKay should apologize for their public criticism of Supreme Court Chief Justice Beverley McLachlin, says an international body of judges and lawyers.

The International Commission of Jurists came to that conclusion following an investigation into the war of words between Harper, MacKay and McLachlin around the ultimately failed appointment of Justice Marc Nadon to the Supreme Court.

A group of Canadian lawyers and academics had asked the ICJ to look into the matter in early May.

In a letter dated Wednesday, ICJ Secretary General Wilder Tayler says there is no evidence to suggest that McLachlin’s intentions in contacting the Prime Minister’s Office and MacKay’s office during the appointment process were intended as anything more than an attempt “to alert them to the possibility that a legal issue could arise” when nominating a candidate from the Federal Court.

Further, Tayler writes, there is no evidence to suggest that McLachlin was trying to offer an opinion about any candidate. When she made the calls, eligibility issues “potentially affected several candidates.”

“Nothing in international standards would render such contact inappropriate,” Tayler writes.

“The ICJ considers that the criticism was not well-founded and amounted to an encroachment upon the independence of the judiciary and integrity of the Chief Justice.”

The ICJ is calling on Harper and MacKay to either publically withdraw their comments or apologize for them.

Nadon was appointed to the top court last fall, but in March the Supreme Court ruled him ineligible because he did not meet the criteria for an appointee from Quebec.

Not long after, Harper went public with McLachlin’s calls to his and MacKay’s offices in July 2013, and suggested that her actions were “inadvisable and inappropriate.”

McLachlin released her own statement to say she wanted to warn MacKay about eligibility concerns, but did not offer an opinion on his candidacy.

Harper and MacKay should never have gone public with their criticism, Tayler writes. If they were concerned about her actions, they should have expressed their reservations in a process that, at least at the start, would remain confidential.

“Such public criticism could only have a negative impact on public confidence in the judicial system and in the moral authority and integrity of the judiciary, and thereby on the independence of the judiciary in Canada,” Tayler writes.

The letter also goes on to suggest that the Canadian government review its process for appointing judges to the Supreme Court to bring it in line with UN principles.

The letter, addressed to University of Manitoba law professor Gerald Heckman, has also been sent to the PMO and to MacKay’s office, Tayler writes.

The ICJ requested comment from the PMO for its review, but Harper’s office did not respond, the letter notes.