THE No.10 Christmas tree was brightened by X Factor stars as the three finalists joined the Prime Minister to turn on the lights.

Jahmene Douglas, James Arthur and Christopher Maloney — plus judge Nicole Scherzinger — helped David Cameron switch on Downing Street’s festive illuminations.

Hundreds of school-children cheered the singers — who will battle it out to win the ITV talent show on Saturday night.

And they warmed up for the showdown alongside the premier with a few Christmas carols.