Katherine Heigl says her efforts to save animals from death row are being sabotaged by a rogue rescue group that’s spreading a whole lot of dog s*** about her foundation … TMZ has learned.

Katherine and her mom, Nancy, run the Jason Heigl Foundation — named after Katherine’s late brother — which supports animal rescue efforts, particularly saving animals from kill shelters. Awesome work, for sure.

Now, according to a new lawsuit, the Heigls’ org signed a deal to support The Pitty Committee, which is a Santa Monica-based dog rescue. The deal was Katherine’s foundation would give TPC $5,000 per month to rescue a minimum number of pups of Katherine and Nancy’s choosing.

When their year-long contract ended in December 2023, Heigl decided not to renew and simply moved on. However, Katherine says a year later, TPC exec Alyssa Deetman jumped on social media and claimed the Heigls owed TPC hundreds of thousands of dollars.

Katherine says the post also accused her of putting dogs in small cages, and even being responsible for the deaths of 2 puppies.

In the suit, the Heigl says Deetman sang a much different tune when she wanted to renew the deal and get more money. They say she emailed Nancy … “I will sing your praises always … I am so proud of the work [the foundation] does. I respect you, and I respect [Katherine] and I know the work you guys do.”