Cameron said hydraulic fracturing -- a controversial extraction method -- could bring cheaper gas prices, as he compared the number of wells being drilled in the European Union to the United States.
A test drill in the countryside of Sussex, southeast England, has attracted a protest camp of hundreds, becoming the focus of a national campaign against the technique.
Cameron said Europe's take-up of the technique compared unfavourably with the United States, where fracking has created an energy boom.
"The EU has about three-quarters as much shale gas as the US so we are missing out big time at the moment and I want to make sure that Britain does not miss out."
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Last month, French President Francois Hollande ruled out shale gas exploration during his term in office.
Fracking has also been the subject of fierce debate in Germany, where Chancellor Angela Merkel's conservatives dropped plans in June for a draft law on the technique amid concerns by some coalition allies.
It also believes the US shale gas boom shows it could reduce energy imports -- which have reached record highs in Britain -- and bring down household fuel bills.
"We would be making a big mistake as a nation if we did not think hard about how to encourage fracking and cheaper prices right here in the UK," Cameron said.
In the United States, "their energy costs in business and their gas prices are half the level of ours".
Fracking involves using huge amounts of pressurised water mixed with chemicals to crack open shale -- sedimentary rock containing hydrocarbons -- to release natural gas.