This has been brought up ooodles of times, SEVEN.
To show that the assertions are correct you will have to start by defining information. There are threads for that.
You could add to:
Complex Specified Information (CSI)CSI and EvolutionCSI and Design
Without that definition there is no meaning to what you have asserted.
There is, of course, a formal definition of "information" as given in information theory. However, using that information it is easy to show that mutations can increase information.
In addition, there is a bit of a logical problem with your assertion.
If a mutation happens that is by your definition (whatever it is) and it is a loss of information then a mutation that sets the gennome back to where it was is, by your definition (whatever it is) a gain in information.
So a mutation that removes a base pair you might define as a loss but a base pair can be added by a mutation for example.
Would you care to elaborate on what the heck you and your source is talking about. Again I suggest adding it to one of the above threads.