Ofcom research reveals rise of tablets has helped drive increase.
Internet use among 16 to 24-year-olds has almost tripled since 2005, according to Ofcom research.
The Media Use and Attitudes 2015 report found that by the end of 2014, young people used the internet for 27 hours and 36 minutes per week. This compared with 10 hours and 24 minutes in 2005.
The average adult user also more than doubled their internet use, which reached 20 hours and 30 minutes compared to 9 hours and 54 minutes in 2005. 2014 saw a particularly fast increase in time spent online, with the weekly internet usage going up three and a half hours from 2013.
In addition, the report saw the proportion of adults using the internet rise from six in ten in 2005 to almost nine in ten today. Ofcom attributed much of the growth to the rise of tablets, with the iPad first appearing in the UK in 2010. Tablets are now used by four in ten adults to go online.
The research also found that 27 percent of internet users regularly watch TV or films online, compared to one in ten in 2007.
People are generally less concerned about the internet: the proportion of internet users saying they are concerned about the internet has fallen from around 70 percent in 2005 to 51 percent in 2014.
"Over the last ten years internet use has increased substantially, both at home and elsewhere," the report reads. "One of the most salient changes over the last ten years has been the way in which people access the internet and consume online content, driven by several inter-related factors including evolutions in technology, infrastructure, cost/price, attitudes, etc."