Laying 'laminate' on existing new carpet underlay

[Arthur Cider]

Is it OK to Lay 'laminate' on existing new carpet underlay rather than pulling up and relaying

 

[Beans-on-Toast]

I have seen laminates laid on top of carpet, let alone underlay. Some mothers like doing this as it gives a springy surface for toddlers. although the laminate manufacturers obviously recommend using their own underlays.

As long as you expect a slightly springy floor I can see no reason why not

 

[WoodYouLike]

Is it OK to Lay 'laminate' on existing new carpet underlay rather than pulling up and relaying

Have you ever seen the dirt, dust and buggies in existing carpet underlayment? Bhhhhh. Can get mouldy after a while too.

And besides that, carpet underlayment is normally made of some kind of rubber, which tends to crumble underneath wooden flooring.
It's up to you of course, but I 'wood' remove the carpet underlayment (don't forget the grippers!) and use proper wooden flooring underlayment.