Portia de Rossi nee Amanda Lee Rogers apparently took a step down the lesbo ladder and is now banging Ellen DeGeneres.

WWW- TITILLATING TV stars Ellen DeGeneres and Portia de Rossi are shacking up after ditching their longtime lady loves.

On Friday it was reported that DeGeneres had split with her girlfriend of four years, photographer-director Alexandra Hedison.

We’re told the real reason for the break is that DeGeneres is now deeply in love with de Rossi, the Australian-born “Arrested Development” diva. De Rossi recently dumped her longtime gal pal, singer-songwriter Francesca Gregorini (Ringo Starr’s stepdaughter) to be with DeGeneres, a source close to the new couple told PAGE SIX’s Jared Paul Stern. The pair are now in DeGeneres’ house in the Hollywood Hills which Hedison left a couple weeks ago.

DeGeneres, 46, and de Rossi, 31, first met nine months ago on a photo shoot, we’re told. They fell “instantly in love,” de Rossi gushed to pals at the time. But DeGeneres remained loyal to Hedison, whom she often credited with “saving her life” at a time of crisis. However, when DeGeneres and de Rossi met up again at VH1’s “Big in ’04” awards gala in L.A. on Dec. 1, events took their natural course.

Their respective girlfriends were absent, and this time there was no stopping the lusty ladies. They managed to find a private spot and “things got so hot and heavy between them that they raced to a limo and fooled around for hours,” our source reports.

The very next day de Rossi left Gregorini, saying she was madly in love with DeGeneres, and DeGeneres asked Hedison to move out of their house, though we’re told the pair plan to make it seem they were already single in order to minimize the fallout.

Reps for DeGeneres and de Rossi could not be reached for comment.

“Alexandra and Francesca are both devastated,” says a source close to the women. “Neither of them had any idea what was coming.”

There is obviously some bitterness, and while some friends speculate that DeGeneres and de Rossi were secretly seeing each ever since they first met, others snipe that de Rossi is out for all the publicity she can get with a new high-profile relationship.

“People who know Ellen well feel she is going through a midlife crisis, dumping Alexandra for a hot, younger woman,” says our snitch. “They predict Ellen will come to her senses and dump Portia to go back to Alexandra in the near future.”