TalkTalk and Three have called on Ofcom to limit the amount of mobile spectrum a single network can own.
The regulator is auctioning off additional mobile spectrum later this year and TalkTalk is concerned that it could go to BT/EE, which already has a 42 per cent stake.
This, it warned, could lead to competitors such as Three, O2 and Vodafone being squeezed out.
Furthermore, TalkTalk believes regular buffering would become more likely, as mobile networks would "struggle to cope with internet streaming".
"Resulting frustrations [would] be exacerbated by a lack of network choice and a higher service price," it said.
TalkTalk has therefore thrown its weight behind the Make the Air Fair campaign launched by Three, which is calling on Ofcom to impose a rule stating that no mobile network should own more than 30 per cent of the UK's mobile spectrum.
"A 30 per cent cap would level the playing field and help keep prices down by making sure UK consumers can choose between competitive mobile deals," TalkTalk said.
"An Ofcom decision on spectrum can help underpin the UK’s drive towards a digital future."
TalkTalk stated that the more spectrum a mobile network operator holds, the more capacity it has to deliver "better, faster and more reliable services to their customers".
However, it said a monopoly on these airwaves would inhibit competition, block innovation and lead to unfair pricing strategies.
Dave Dyson, Chief Executive of Three UK, added that consumers are worried about the "massive imbalance in ownership of the nation’s airwaves".
"Over 60 per cent of UK consumers fear that reduced competition between service providers will lead to increased prices," he commented.
"Ofcom needs to act on these concerns."
“UK mobile customers face higher prices, slower speeds and worse coverage in future."
This comes shortly after the European Union backed proposals for a rollout of the 700MHz spectrum band to boost mobile broadband speeds across the bloc.
Policymakers backed the move as this particular spectrum band requires less infrastructure than higher bands, while it can also cover wider areas.
This should improve both access to mobile broadband throughout the EU and connection speeds, as well as pave the way for next-generation 5G mobile technology to be rolled out more widely.