The 43-year-old actor faced a backlash after his comments were made known. Picture: Reuters

Dax Shepard was forced to come clean about Santa Claus after his eldest daughter started "asking questions".

The Parenthood actor has a "fundamental rule" that he will not lie to his daughters - Lincoln, five, and Delta, four - and so had to tell them the truth about Father Christmas after Lincoln told him the story of Santa didn't make sense.

He told Us Weekly magazine: "I have a fundamental rule that I will never lie to them, which is challenging at times. Our five-year-old started asking questions like, 'Well, this doesn't make sense, and that doesn't make sense.' I'm like, 'You know what? This is just a fun thing we pretend while it's Christmas.'"

The 43-year-old actor faced a backlash after his comments were made known and he took to his podcast to further explain just how it had all come about and how he just couldn't "ignore" his daughter's "critical thinking".

Speaking on his Armchair Expert podcast, he said: "So here's what happened for me: I explained the concept to her, and ... leading up to Christmas last year, she started poking holes in the logic ... 

"First it was, 'Well, how does he go to every house?' Then it was, 'How does he fit down the chimney?,' then it was ... all these different things, and I was going along, going with the standard lies you tell [to keep them believing in Santa], and at a certain point, I was looking at her little face, and she had this critical mind that was finding holes in the logic. And I was basically forcing her to ignore her critical thinking!"