Its aim is to celebrate the LGBT+ community at Engine, which owns PR agencies MHP and Mischief, among others. Members of the network will also work alongside Engine's HR and management teams on policy. There will be a series of events and talks, with staff sharing personal stories and messages on Twitter with the hashtag #EnginePride.
A rainbow-striped installation of thousands of post-it notes has been created in celebration of the network. It will remain in place on the side of Engine's Great Portland Street offices in London from today until the Pride in London parade takes place this weekend.
It ties in with the wider Pride in London campaign Love Happens Here, which was created by WCRS (see video below), Engine said.
Mark Harrop, a social strategist at ad agency WCRS and network founding member, said: "I know what a difference working in an inclusive environment makes, and I am glad Engine is flying the flag for the industry.
"No one should come to work and feel like they do not belong, which is why it is important that networks like this exist at Engine and across other agencies. It's amazing we can make a difference in our own way."
Engine LGBT+ is part of the agency's wider commitment to nurturing diversity, it said. Initiatives have so far included a policy to create gender-balanced shortlists for all senior roles and "compulsory unconscious bias training" - which is designed to make staff aware of how unconscious factors affect the way people behave at work, a spokesman for Engine said.