BT has just got into a row with analyst firm Ovum over the size of its VoIP market share.

BT announced recently that it had gained one million VoIP customers. However, as with another recent announcement, this time on the number of homes with broadband, BT has been accused of not telling the entire truth - "loosely worded" is how one analyst coyly described it. And in doing so, he provoked a full-scale rebuttal from BT.

BT's release trumpeted its success in gaining VoIP customers by saying that it now had over a million registered customers "for its VoIP services, BT Broadband Talk and BT Softphone, representing more than a third of BT’s consumer broadband base."

The company added: "BT has reached this key milestone more than six months earlier than projected, having set out in July 2006 a target of achieving a million VoIP customers within twelve months."

Research and analysis firm Ovum however said that "anyone who signs up for BT Retail's Total Broadband package is automatically registered for VoIP even if they don't use the service."

Ovum analyst Mark Main said: "Yesterday's announcement needs a little dissecting. In the VoIP market the devil is very much in the detail. VoIP is now increasingly bundled by operators and it is hard to analyse precisely how many customers are really using the service in earnest and how many have merely used it a few times - or possibly even never.

"BT's statement is worded rather loosely - it implies that BT has a million VoIP users, whereas in reality anyone who takes a BT Retail Total Broadband package is automatically registered for VoIP even if they don't use the service."

Main posited an explanation of BT's reasoning: "With VoIP being a marginal cost business, it makes sense for operators to do this, as it makes a very good impression in what is starting to be a competitive VoIP market. Automatic activation of VoIP also avoids future customer contact which merely creates unnecessary cost. It also pre-deploys the necessary hardware on customers' premises which will help to defend against churn.

"With these customer numbers, we think BT has a small overall market lead but as more players enter the market it will be increasingly difficult to sustain."

BT rebutted the claim that it was bundling customers of its Total Broadband package into the VoIP numbers. Spokesman Adam Liversage said that, as a responsible, publicly quoted corporation, BT doesn't make up its figures. He said: "Ovum have got it completely incorrect. Customers have to go through a separate process to sign up to VoIP -- it's an additional package that allows you make calls free during the day and you have to set up a separate account."

Liversage said that BT's release didn't go into that level of detail in its announcement "or would have been a very long release".

He also questioned Ovum's statement regarding BT's market share, saying that since the company's major competitors - he cited Orange and Skype - don't quote the size of their registered user base, market share figures are close to impossible to determine.

Main responded: "I have first-hand knowledge of a BT Total Broadband customer who was subscribed to the VoIP service on joining BT Total Broadband without explicitly requesting it. On that basis it seemed unlikely to me that it is an isolated case.

"I collect and analyse market data from conferences, company reports, off-the-record discussions and other useful sources. I then make what I consider to be reasonably good estimates of numerous company's market presence based on growth in the UK market and other similar markets. Part of my job as an analyst is to do this for Ovum clients and I do it on a fairly regular basis.

"Depending which VoIP service types and operators you choose to include I believe I can then make reasonable comparisons. Since BT's figure of one million includes both its BT Softphone and Broadband Talk customers, I chose to include in the comparison my estimate of Skype's regular users - which is in the same order of magnitude as BT's total."