Google CEO Sundar Pichai has promised a "much harder line on inappropriate behaviour," less than a week after revealing the tech giant fired 48 staff over sexual harassment claims in the last two years.

In a memo to staff obtained by news website Axios and CNBC, Pichai conceded that the company's apology at a weekly meeting with employees last Friday "didn't come through, and it wasn't enough."

Google declined to comment on the reports.

The Tuesday memo followed another internal email sent by Pichai and vice president of people operations Eileen Naughton saying that 48 people, including 13 senior managers, have been terminated for sexual harassment in the past two years.

The email was sent in response to a New York Times report alleging that the Silicon Valley company had dismissed Android creator Andy Rubin for sexual misconduct in 2014 and is still paying him a package worth 90 million dollars.

In the Tuesday memo, Pichai admitted that the steps taken by Google so far to counter inappropriate behaviour were not enough and that he knew "our work is still not done."

"I understand the anger and disappointment that many of you feel. I feel it as well, and I am fully committed to making progress," Pichai said.

He also specified that the internet giant had not provided exit packages to any of the 48 people who were fired.

Pichai also said that employees planning to protest on Thursday would have the "support" they needed and that Naughton would make sure that managers are "aware of the activities planned for Thursday."