Faced with growing criticism that his company’s best known products and services may be biased by its employees’ political views, Google Chief Executive Sundar Pichai has urged those who work at the internet giant to keep their opinions on politics to themselves.

According to the Wall Street Journal, Pichai sent a memo to Google’s employees, also known as “Googlers”, on Friday warning them to that if they do anything that “undermines (users’) trust, we will hold them accountable.”

“We do not bias our products to favor any political agenda,” Pichai said, in a copy of the memo that Journal said it obtained. “The trust our users place in us is our greatest asset and we must always protect it.”

Pichai’s laying down of the law regarding employees’ political bias in their work comes after the leaking to the public of some discussions by Google employees that appeared to show those workers lamenting the policies and administration of President Donald Trump.

Among the matters that the Journal said Google employees talked about was President Trump’s January 2017 travel ban, and ways that they could alter Google search functions to connect people to organizations and efforts opposed to the travel ban.

In his memo, Pichai said no such changes were put in place.

“Recent news stories reference an internal email to suggest that we would compromise the integrity of our search results for a political end,” the Journal reported Pichai as saying in the memo. “This is absolutely false.”

Last month, President Trump, took to Twitter to call out Google for what he said was promoting stories critical about his presidency and tamping down reports by more friendly outlets. Trump called the actions a “very serious situation” that “will be addressed.”