Around 86 percent of participants in a British poll conducted by The Sun voted in favour of legalising the substance.
A report from the Commons Home Affairs committee had urged a shake-up in the country's drug laws, which would even decriminalise heroin, The Sun reported.
"I don't support decriminalisation. Drugs use is coming down, the emphasis on treatment is absolutely right - and we need to continue with that to make sure we make a difference. Also, we need to do more to keep drugs out of our prison," Cameron said.
"These are the government's priorities."
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Cameron also rejected calls for a Royal Commission to launch an inquiry into Britain's drugs laws.
US states Colorado and Washington have passed legislation to legalise the recreational use of marijuana.
