Muir told HR magazine because good business ethics is about culture, leadership, values and principles, HR should be at the "very heart" of this message.
He was speaking to HR magazine after authoring a report, which looked at how boards provide ethical leadership, how they monitor the tone they are setting and how non-executive directors check that their company has a good ethical compass.
The study, Tone from the top, published by Keeldeep Associates Limited, which was founded by Muir and sponsored by Ashridge Business School, found improving ethical business starts with a "good board" made by a "good chairman".
Bad ethical practices
The study stated that in 2013 many companies had weaknesses in business ethics, and there are few sectors that can claim the moral high ground. There was the repercussions of PPI mis-selling, Libor manipulation and the horsemeat scandal.
Google and Amazon faced a parliamentary committee probe into their accounting practices. HSBC was fined $2 billion for allowing money laundering in central America and the BBC was investigated after excessive payoffs to executives. There was also the NHS mid-Staffordshire and phone-hacking scandals.
Muir, who has worked at the highest levels of HR for more than 20 years, said because businesses now operate in a more transparent world, they must think carefully about the ethical tone they set from the top.
"All the chairman I spoke to for the report now accept that ethics are high up the business agenda," he told HR. "Previously boards were more distant, aloof, more of a federal structure, but now boards are much closer to management."
Keeping it fresh
Muir said the problem many boards face is how to keep the message fresh and keep sending out the right signals. He said this is where HR can play an important role.
"Delivering the message of good business ethics is a hugely important role, but I suspect a number of HR directors haven't grasped the importance of their contribution," Muir said.
"It's a golden opportunity for HR because it's about culture, it's about leadership, values, the principles and the way in which companies do things.
"I think a number of HR directors need to get closer to the chairman of the company, and build a stronger relationship with the non-executive directors (NEDs), and help them the board get closer with line managers.
"Sadly, I've met some HRDs who can't even name their NEDs. So it's incumbent upon HRDs to have a very strong and effective working relationship with every NED."
Ethical risk
The study found ethical risk is similar to commercial risk in that it cannot be fully eliminated. However, businesses can minimise it and HR can help by identifying the sources: Bad apples - people with inappropriate morals. Foolish apples - people who unthinkingly do the wrong thing. Pressured apples - people who are in a situation that tempts them in to do the wrong thing.
HR must strengthen recruitment and assessment processes, and improve training to build moral backbone, the report stated.
Muir also said it's important HR encourages strong employee voice and ensures every worker in the organisation is getting behind any culture change.
"There is a problem where some employees start thinking, 'we have to do all this extra work to help the top people look good'," he said. "So the challenge for HR is how do you remove that cynical view and help employees understand that ethical practice must be part of the DNA, not just for the health but for the survival of the organisation."
Muir added: "The tone from the top is important to encourage employees to speak out against bad practice. The climate set by management is the biggest influence over how confident people are to speak up and speak out, if it's a climate of fear then they won't speak out, and the company will ultimately run into problems.
"If it's one of openness, candor, honesty and enables employees to have a voice then that's a very healthy sign."
Inside HR executive club
Ian Muir launched the report last week at the 'Inside HR Executive Club' organised by recruitment firm Reed. The purpose of the club is to provide trusted and confidential support for HR leaders, and also provide them with a platform to share ideas and objectives.
