DAVID CAMERON: The EU referendum is bigger than a general election
If voters don't like a government they can kick them out after five years but reversing a decision to leave the EU would be "very very difficult," Cameron said.
He said the shock to the economy of a Brexit would be severe.
Leaving the European Union could add £220 a year onto each household's food bill, said in an interview with ITV's Robert Peston.
Cameron said that supermarket bosses warned "prices would go up if we left the EU because there'd be a shock to the economy, the pound would fall, and that would mean the prices we pay in this economy would be higher, particularly for food because we import so much."
"Is it worth taking this risk? I, as Prime Minister of this country, absolutely believe it is not worth the risk of taking this step," Cameron said.
The probability of Britain voting to leave the European Union on June 23 is currently less than 20%, according to polling analyst Matt Singh.
Singh, the polling analyst behind Number Cruncher Politics (NCP), said in his latest blog post that while some of the results of polls published this week have been dramatically varied, they don't change the overall picture of Remain being the most likely victors.
In fact, according to his updated forecast, the probability of Britain voting to leave the EU is just 19.6%.
Cameron also criticized remarks on banning Muslims from the US made by Republican Presidential Candidate Donald Trump, calling them "wrong and divisive" as well as "dangerous."