'Massive' Christmas Quarrel for Katy Perry and Russell Brand?

By Kat Giantis

For months, Katy Perry and Russell Brand have adamantly denied reports of domestic trouble, insisting all is well in their year-plus marriage. But eyebrows were once again raised after they reportedly spent Christmas 7000 miles apart, with the popster frolicking in the Hawaiian surf and the British funnyman hanging with pals in the much different seaside setting of Cornwall, England.

The supposed reason for their separate celebrations: a Christmas quarrel.

"They had a massive fight," a source tattles to Us Weekly. "She was like, '[Bleep] you. I'm going to do my own thing.' Russell replied, 'Fine, [bleep] you, too.'"

(And now we know who ended up on Santa's naughty list. Anyhoo, moving on ...)

According to the mag, Katy's original plan was to fly with her family to London on a private jet to mark the birth of the baby Jesus with her hubby. But after the alleged argument, she decided instead to head to Kauai with some friends.

Perry, 27, didn't appear bothered by the absence of Brand, 36, on her tropical getaway, taking a Christmas Day dip in a teeny-weeny bikini. She was also without her wedding ring, although she could have simply removed it ahead of her swim.

"They haven't split up just yet, but things are not good," maintains the insider. "The fighting is getting worse."

So, what are they squabbling about? Click on for more ...