Figures released by the Office for National Statistics (ONS) show that men in London earned on average 13.2% more than women in 2013, up from 10.9% one year previously.
Nawrockyi told HR magazine the figures demonstrate we still "don't have equality" and called for employers to do more to address the problem.
"The gap has been steadily closing for a number of years now, so this could be a blip," she said. "But the fact that there is a pay gap at all is disheartening. One thing we think would really help is if organisations make their pay data public."
She added that she hopes companies will do this voluntarily without the need for legislation.
"It's more credible if employers feel empowered to act rather than being beaten into submission," she continued. "Putting the data in the public domain is a good way to encourage openness and transparency. It would be a good way to eradicate bias, both conscious and unconscious."
Labour MP and shadow minister for women and equalities Gloria de Piero said that "equal pay should be a priority for all employers".
"Whether you’re a chief executive or hairdresser, women across the capital are being paid less than men for doing the same or equivalent work," she said.