The two sides meet at Twickenham in the Six Nations this weekend, with the Azzurri having never beaten the Red Rose.
However, Barritt believes that the Italians' opening match win over France demonstrates that they are a force to be reckoned with.
"I think Italy have proved over the last couple of seasons that they can't be underestimated," Barritt told Sky Sports News.
"We certainly won't be looking past them. We will prepare as we would for any side in the world, you can't afford not to.
"We have to take it week by week. Our focus is on Italy for now just as our focus was solely on the France game last time. All our attention has to be on this game."
A win over Italy would set up England for a Grand Slam showdown against Wales on the final weekend.