Mobile voice-over-IP (VoIP) is starting to gain traction, and will soon offer a direct challenge to traditional mobile operators, according to a recent report from analyst firm Gartner.

The growing adoption of flat rate mobile data packages has led the technology to take a significant slice of the $692bn (£460bn) global mobile voice market.

Gartner's Emerging Technology Analysis: Mobile VoIP, Global Consumer Communications Services report said that operators still have between five and eight years before mobile VoIP fulfils its full potential.

"Mass-scale adoption of end-to-end mobile VoIP calling will not happen until fourth-generation networks are fully implemented in 2017," said Tole Hart, research director at Gartner.

"Once the basic market conditions are in place, transition to mobile portal VoIP should be fairly rapid because of the inherent convenience and end-user cost savings."

The rapid development and uptake of smartphones has seen several VoIP providers, such as Skype, Truphone and Fring, develop applications for the majority of mobile operating systems for use over Wi-Fi or the mobile operators' voice networks.

These applications have avoided relying too much on 3G data connections due largely to the inconsistencies in the level of service, according to Gartner. However, with the advent of 4G networks such as WiMax or LTE, this is set to change.

"Ten years from now more than half of mobile voice traffic will be carried end-to-end using VoIP," said Akshay Sharma, research director at Gartner.

"Carriers will adopt voice services because of the increased capacity and reduced cost of delivering voice over 4G networks. Third parties will adopt a voice option for their communications hub."

Hart believes that around a third of mobile voice traffic will be carried through third-party mobile portals such as Google, Facebook, MySpace and Yahoo within a decade.

However, the report lists several hurdles that need to be overcome if mobile VoIP is to become ubiquitous over the next few years. Chief among these is the delay in rolling out 4G networks due the current harsh economic climate, and the general plan to install these networks in main cities and build out from there.

Although the transition is expected to be gradual, Gartner warns that operators need to start considering how they are going to approach this issue.

The analyst firm suggests that these telcos start looking at partnering with other types of service provider to make sure they have a way of altering revenue streams as the technology matures and usage habits shift.