Everything LROM said. Social workers see a lot of crazy, scary stuff. Having worked in the field, you never know what you will find when that door opens. You could have a lovely smiling mom in a nice house telling you how all is well and the door opens up to things you can't *unsee*. And when some little thing you are ready to "check out and cross off" turns into "get a warrant" 1.) There is not way I could see *not* getting a warrant/calling the police because the issue still stands and I have no additional information to discredit it. 2.) I get really nervous because I have *no* idea why I am being barred- Is it a boyfriend on the couch who has been skipping parole? Is is some other horrible thing? Or is it a concerned and educated parent exercising their rights? I don't know why, but it's my job to see the kids are safe, so I'm going to do what I need to for the door to open. 3.) Social workers have their own experiences that shape their ideas. So, you remember the child where you missed the signs. You remember the lovely mom you interviewed after "bogus" claims to find horrible things later. And it makes you promise to not let that happen again. So "get a warrant" sends up a million feelings that are not entirely related to what is going on with you (which, you don't really want).
In short, I could not *imagine* if someone said "get a warrant" that I would *not* do that and most likely, call the police (who CAN come in if there is reason to believe that the children are in danger).
So, while it may be within your rights, I would use that with great seriousness.
But police have to have probably cause, and third party "Someone called and said ....." doesn't constitute probably cause. Yes, they would probably try to get a warrant, but that requires going in front of a judge and asking for one, and then you might get one, or you might not. The CPS call on me was about "she doesn't respond to the baby's cries when someone else is holding him" Ummm...I DO NOT think a judge would have granted a warrant based on that!
Refusal to comply with a police request is often considered probable cause. That is the reason they can arrest you for drinking and driving if you refuse a sobriety test. It's the idea of "if you have nothing to hide then why refuse?"