The opinion that the Nobel Prize in Economics is a "fake" prize is not shared by the Nobel Foundation, which treats it as equal to Nobel's prizes and awards them in the same way, with the same people, by the same criteria as the other science prizes. They differ only in name as they were named after different benefactors. I wish people would stop saying this. On the other hand, it's a sure sign you don't know what you're talking about.
True, using "fake" was just to be pejorative. It is not one of the original Nobel prizes, it doesn't fit the original prize philosophy of Alfred Nobel but it is the only non-Nobel prize that is officially associated with the Nobel Foundation.
The same people (Royal Swedish Academy of Sciences) also award the Crafoord Prize as well as others, but only the Economics one put "Nobel" in the name and the fact that this was done to improve the image of Economics is just history.
I don't think you're being accurate to say they differ "only in name". There is plenty of controversy about the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel being called "The Nobel Prize in Economics". The Nobel family doesn't like their name being attached to it since it wasn't Alfred Nobel that created it. Hayek was given the prize and stated that he, if he had been asked, would have advised against it because "the Nobel Prize confers on an individual an authority which in economics no man ought to possess... This does not matter in the natural sciences. Here the influence exercised by an individual is chiefly an influence on his fellow experts; and they will soon cut him down to size if he exceeds his competence. But the influence of the economist that mainly matters is an influence over laymen: politicians, journalists, civil servants and the public generally". I like that quote because it nicely encapsulates the difference in the fields of hard science and economics and the different effects of this kind of prize.
http://www.nobelprize.org/nobel_prizes/economics/