Vodafone's share of the mobile market has been declining year-on-year but analyst numbers suggest it is still drawing more cash per customer than its competitors.

Quarterly results from Vodafone's head office in London show the mobile operator shed 26,000 customers during the three months to June 30.

Vodafone New Zealand now has 2.46 million customers and is still the country's biggest mobile company.

Based on the latest comparable numbers, Vodafone has around 45.8 per cent of the local market, Telecom has around 40.4 per cent and 2degrees 12.7.

The quarterly slide was Vodafone's biggest since September 30 last year, when the company posted a loss of 35,000 customers.

In the year to June, Vodafone shed a total of 21,000 customers, a drop of around 0.8 per cent.

Between 2009 and 2010, the mobile carrier's customer numbers fell 1.3 per cent.

Forsyth Barr's Guy Hallwright said Vodafone has been taking a hit since 2degrees entered the market in August 2009.

"The numbers have been bouncing around but [Vodafone] has been suffering some erosion of prepaid customers from pretty much immediately after 2degrees started up," Hallwright said.

While agreeing 2degrees will be causing some pain, IDC senior market analyst Rosemary Spragg said mobile operators traditionally had a drop at this time of year.

"It's partly seasonal with the drop of temporary summer prepay [connections] and things like that," Spragg said. "I'm sure a proportion has gone to 2degrees but we'll have a better idea of how much when Telecom announces [its results] in August."

Although Vodafone is losing customers, IDC models suggest the company brings in a good deal more revenue per customer than its rivals, at $43 a month versus Telecom's $26, and 2degrees' $18.

"Vodafone's is significantly higher and that's reflecting its strong business base," Spragg said.

While Telecom is lagging behind Vodafone, Spragg said the company's plans to shift all customers off the CDMA and on to the XT network will give it a boost.

Telecom's CDMA network is being shut down next July. About half of Telecom's customers have migrated to the newer network.

Spragg said Vodafone will also be pleased the percentage of its customers on post-paid (or on-account) plans is growing. Post-paid plans typically draw in more revenue.