Businesses using the "incumbent" mobile operators in London are being short-changed with their performance, with both Vodafone and O2 well behind the performance of Orange, T-Mobile and Three.

Independent testing has shown the 4G service provided by EE, which controls the Orange and T-Mobile brands in the UK, is delivering the best performance in London when it comes to mobile data, voice calls and SME texts.

The EE 4G service launched last year also led to the operator overtaking previous London performance leader Three in the capital. Until the early 1990s businesses only had two mobile operators to choose from - Vodafone and BT Cellnet (later to become O2 and acquired by Spain's Telefonica).

Many companies have stuck with these two networks ever since, and a number have been impressed with Vodafone's widescale international roaming agreements leading to competitively priced business packages. But the fact that Vodafone's performance now lags behind every other provider in the capital marks a bad week for the operator.

It says it has been forced to delay its 4G service launch until "the end of the summer" and will now have to double its infrastructure investment in the UK to help enable it. And as O2 has an infrastructure sharing agreement with Vodafone the pair are set to stay in the slow lane when it comes to serving Londoners' mobile internet needs.

The mobile service tests were carried out by independent testing firm RootMetrics. It said Vodafone, which previously shared the number two ranking, has fallen to last place.

The area tested - known as the London Larger Urban Zone (LUZ) - includes everything from Saffron Walden in the north to Tunbridge Wells in the south, and Southend-on-Sea in the east to Maidenhead in the west.

According to RootMetrics, Vodafone's network reliability - how often users can connect and then consistently use the network - is lower than its competitors. On this front, Vodafone scored 92.3 (out of 100) compared to 97.8 for Three, 97.2 for EE, and 94.6 for O2.

In terms of making calls all operators did well with EE and O2 tied for first place, each with call failure rates of just 1.8 percent and 2.1 percent respectively. Only about two in 100 calls, for example, would not go through for O2 customers.

Vodafone performed worse with 4.8 percent of calls failing to connect - rising to 7.7 percent on commuter routes. Anything over a 5 percent failure rate is considered a poor service, said RootMetrics.

In terms of text message services, again, all operators "did well", RootMetrics said, although Vodafone delivered 88 percent of texts within 10 seconds, compared to Three's 92.9 per cent.

The overall ranking out of 100 for the mobile network providers in London's LUZ:

EE - 92Three - 83O2 - 81Vodafone - 72

One has to consider of course that the 4G service offered by EE - the only one available at the moment - is more expensive to use. But Three, a network operator which only appeared in 2000 after the government 3G spectrum auction, is ahead of O2 and well ahead of Vodafone.

"Our testers conducted more than 83,211 tests to deliver a highly accurate picture of mobile network performance in the area," said RootMetrics CEO Bill Moore.

"While all operators have broadly upped their game in the last eight months, some have achieved less than others, leading to a major reordering of the rankings. Londoners may not think that the service provided by a mobile network can shift so dramatically so quickly."