Three Republican senators in the US have written to Google chief executive Sundar Pichai asking him to provide a copy of an internal memo that was claimed to have cited regulatory fears as a reason for the company withholding details about a major data leak in the Google+ social network.

Alphabet, the parent company of Google, will shut down the Google+ social network after confirming on Monday that data from up to half a million user accounts may have leaked due to a bug in the system.

Google's plan to launch a censored search engine in China has attracted attention from the US Government, with Vice-President Mike Pence calling on the company to drop the plan.