Missing Gwen? Blake Already Embroiled In 'Bitter' Feud With Xtina On 'The Voice' Set

Tensions were high last night when The Voice returned for Season 10 — but it wasn't the contestants who were on edge!

RadarOnline.com has exclusively learned that Blake Shelton and Christina Aguilera — who replaced the country superstar's girlfriend, Gwen Stefani, 46, on the panel this season — are already at each other's throats.

Shelton, 39, "hates the fact that Gwen is no longer with him this season," an onset source told RadarOnline.com. "Everyone knows this and he is taking it out on Christina, and they are not getting a long at all."

"It's his mission to make this as uncomfortable as possible for her so that she will not want to return next season," added the source.

As RadarOnline.com previously reported, Shelton contemplated leaving the show after 35-year-old "Dirty" singer Aguilera confirmed that she would be returning this season, along with judges Adam Levine, 36, and Pharrell Williams, 42.

"The execs knew that Blake was bluffing, thankfully," a source noted at the time. "This is such a huge source of income for Blake and America loves him, so they came up with a plan to bring Gwen back on as a mentor on Blake's team."

So how has Aguilera dealt with Shelton's shade-throwing?

"Christina is acting her normal self," said the source, which means that "she's been a diva."

"That's just who she is and nothing has really changed between this season and past seasons that she's been on."

Do you think that Christina is a better judge on The Voice than Gwen? Sound off with your opinion in the comments below.