News of the accidental spamming came as Google revealed it is working on a business-focused feature for the Google+ social networking service.
Notifications from the service went out multiple times to users due to a bug in the code after the service's notification system ran out of disk space at the weekend.
Vic Gundotra, senior vice-president of social for Google, posted an apology on his Google+ account.
"Please accept our apologies for the spam we caused this afternoon.For about 80 minutes we ran out of disk space on the service that keeps track of notifications. Hence our system continued to try sending notifications. Over, and over again. Yikes," Vic Gundotra said.
Gundotra's admission that the Google+ team failed to plan for hitting such high volumes came alongside news that developers are preparing to gear up the service for business use.
The business tools, aimed to compete with rivals LinkedIn and Facebook's company pages, will be available later this year, according to Bloomberg.
Google plans to include analytics and links to other services that businesses might use, such as Google's AdWords advertising system for internet searches.
As demonstrated by the notification glitch at the weekend, Google has struggled to handle demand for Google+, which is available on an invitation-only basis during its testing phase.
Google has recommended that businesses do not create Google+ accounts with the current consumer version, but instead wait for the business version.
The conservative limited access testing approach has been praised by privacy groups after the privacy failures of Google's Buzz and Street View services.
Google president Eric Schmidt has indicated that Google plans to make privacy a differentiator for its Google+ social networking service.
Last week, Eric Schmidt said Google+ has a different approach to privacy from rivals such as Facebook, which has been criticised for its policy of enabling content-sharing features by default.
This story was first published on Computer Weekly