The first-time dad wrote on his Facebook page:"There are NEVER diaper changing stations in men's public restrooms. The first public men's room that I go into that has one gets a free shout out on my FB page! #BeTheChange"
The message hit a chord with parents on Facebook and quickly received more than 200,000 likes, with people commenting that the double standard makes it harder for dads to look after their babies on days out.
"Ashton every one is talking about this now! It wonderful mothers and fathers have been complaining for years... And I'm so glad because of you they are finally listening," wrote one commenter.
Another suggested that Ashton should use Wyatt's next nappy change to stage a protest: "I say spread a blanket out on the table and change her there, maybe they will get the hint!"
Ashton and Mila Kunis's daughter Wyatt is now five months old, and while Ashton and Mila have both become dab hands at nappy changing, Mila's mother has been floored by the disposable cartoon-covered variety.
Mila appeared on Jimmy Kimmel Live and described her mother's amazement at the ingenuity of the new-fangled invention.
Mila said: "She was like, 'I don't understand what this is. What do I do?' I was like, 'Mummy, you lift the baby up, stick it under, and Velcro.' 'And then just throw in the trash?' I was like, 'Away it goes!' And she was like, 'Well, if I had this, I would just have seven babies. This is amazing!'"