Several current and former Google employees are publicly criticising an employee-written memo that suggested the lower numbers of women in the tech industry are due to biological differences, a view that sparked outrage at the internet giant and inflamed tensions over sexual harassment and discrimination in Silicon Valley.

The unnamed engineer asserted in the 3000-word document that circulated inside the company last week that "Google's left bias has created a politically correct monoculture" which prevented honest discussion of the issue.

"Distribution of preferences and abilities of men and women differ in part due to biological causes and that these differences may explain why we don't see equal representation of women in tech and leadership," he wrote.

The memo stoked the heated debate over treatment of women in the male-dominated Silicon Valley that has boiled for months following sexual harassment scandals at Uber and several venture capital firms.

Google's recently hired vice president of diversity, integrity and governance, Danielle Brown, sent a memo in response to the furor, saying the engineer's essay "advanced incorrect assumptions about gender."

"Part of building an open, inclusive environment means fostering a culture in which those with alternative views, including different political views, feel safe sharing their opinions," Brown wrote.

"But that discourse needs to work alongside the principles of equal employment found in our Code of Conduct, policies, and anti-discrimination laws," she added.

Google engineering vice president Aristotle Balogh also wrote an internal post criticising the employee's memo, saying "stereotyping and harmful assumptions" could not be allowed to play any part in the company's culture.

A Google spokesperson said that the statements from Brown and Balogh were official responses from Google.

Yonatan Zunger, who has said he recently left his job as a distinguished engineer on Google's privacy team, wrote on blogging website Medium that the unnamed engineer does not appear to understand gender, or engineering.

"All of these traits which the manifesto described as "female" are the core traits which make someone successful at engineering", Zunger wrote. 

"Essentially, engineering is all about cooperation, collaboration, and empathy for both your colleagues and your customers".

Worst of all, the nameless author "does not appear to understand the consequences of what he wrote, either for others or himself", Zunger wrote, adding that if the engineer reported to him he'd be fired.

Sarah Adams, a software engineer at Google and founder of Women Who Go, a community for female coders, said on Twitter the memo is indicative of a problem that goes beyond its author.

Rajan Patel, a senior engineering director at Google and a statistics instructor at Stanford University, said he wrote a note to Google colleagues denouncing the memo.

There were also expressions of support for the anonymous engineer. He said in a comment on his original posting that he had received "many personal messages from fellow Googlers expressing their gratitude for bringing up these very important issues," according to a copy of the memo posted by technology news site Gizmodo.

Agencies