The firm joins the likes of Vodafone, who also believe the decision will put EE at an unfair advantage, as most network providers won’t be offering 4G until next year.
As reported by T3 earlier this month, Ofcom gave Everything Everywhere the green light to offer the super-fast fourth-generation mobile broadband to customers using its existing infrastructure.
At the time, an O2 spokesperson said: "We are hugely disappointed with today’s announcement, which will mean the majority of consumers will be excluded from the first wave of digital services. This decision undermines the competitive environment for 4G in the UK."
Now the firm is looking to block the network’s 4G launch by lodging an appeal with the Competition Appeals Tribunal.
This follows on from a complaint O2 reportedly sent to both Ofcom and culture secretary Jeremy Hunt, who has been overseeing the 4G UK rollout.
O2's complaint won’t go down well with consumers or smartphone manufactures, both of whom have been calling for 4G services to be introduced to the UK for some time.
Apple may also be a tad cross, as the firm is rumoured to be launching a 4G-ready iPhone 5 this month.
We're yet to hear further comment from O2 but will keep you posted as and when we do.