Quiet squeaking when pressing or releasing accelerator pedal

Well the problem is stated in header.

Additional info: sound like old baby carriage or ungreased cart, very quiet, if conditioning is on, you probably wont hear it. Sound appears when car moved some distance, not after begining of journey. I'm pretty sure that sound come from passenger (right side), but my wife says that it comes from center/driver side.

Now I have two possible versions:

1) old brake discs, 50000+ km (or may be some dirt?)
2) might it be inverter dying?

Anybody heard sound like this?

I have the same, no idea what it is. When releasing the brake the whole car sqeeks.

It could be that the pivot for the pedal needs lubricating.

Or, when the brake pads are low the warning according to the manual is a squeeling sound. I have never heard this but would have thought that you might hear it as you move away before the pads have retracted slightly, but more likely when you apply the brakes.