Knowles said leaders must ensure diversity policies and strategies are in place and they are "aligned with every other part of the business".
He was speaking about how to best balance your business to achieve success at the Women's Business Forum in London yesterday.
Knowles said he was encouraged to see women "increasingly" play a more important role at the top levels of business.
"A balanced business accelerates success and is a major source of competitive advantage," he said. "It's important to have an inclusive culture and changing that starts at the very top.
"You must have policies in place for this to happen though. If you don't you're not allowing your organisation to properly recruit, reward and performance manage your female talent.
"The people who are actually responsible for changing the culture and promoting diversity have got to be the ultimate leader of that business."
Hitting targets
Also speaking at the event was Kirsty Bashforth, group head of organisational effectiveness at BP.
She told HR magazine that BP has set itself a goal of 25% of its board members to be women by 2020. Their current level is 17.5% with a global employee base of 85,000.
Bashforth said diversity needs to be driven from the top, but line managers have an important role to play.
"Diversity can be driven by our senior leaders but it's also down to strong line management," she said. "We must teach our line managers to be curious and for them to have the right conversations at all stages of the interview process."