The survey, which was commissioned by O2, also named O2 as the fastest mobile network when it came to downloading music files.
SIRODA tested web browsing on all five of the UK's mobile networks in 150 locations over 60 days and at a number of different times during the day.
The organisation said this was in a bid to replicate usage patterns and gain a realistic picture of speeds mobile users are getting.
"This week's independent study by O2 is a welcome endorsement of Vodafone having the best network in the UK," said Guy Laurence, CEO of Vodafone.
"We're seeing continued high demand for our range of smartphones, including the iPhone, driven by customers enjoying a great experience from our outstanding network."
- Compare best mobile phone deals
- Smartphone buying advice
- See all smartphone reviews
- Explore the virtual BlackBerry