Italy could be in for another political shake-up.

LISTEN ABOVE: Italy correspondent Sabina Castelfranco speaks to Rachel Smalley 

Italians are voting in a crucial referendum to change the constitution which was first drafted in 1948.

Prime Minister Matteo Renzi has made promises to stimulate the country's sluggish economy and streamline its laws.

The change would weaken the upper house of Italy's parliament by cutting its numbers from 315 to 100, and limit their powers to allow laws to be pushed through more quickly.

Correspondent Sabina Castelfranco told Rachel Smalley it's too close to call if it will be a yes or no vote.

"It's very similar, I think, to what we saw with the Brexit vote and with the Trump vote. It's really a question of waiting until these polls close tonight and during the night we're expected to get some idea of where this is all going."

CNN's Nina dos Santos said the Prime Minister's indicated he'll resign if it doesn't go his way.

"That could precipitate another wave of transitional governments, could usher in an era of technocratic governments that we've already seen in the last five years, at least once."