Hi, Newbie so be gentle please

I'm working in a large organisation into a General Manager who is about to move to another area of the business, with likely some months needed to recruit and replace him.

In the meantime I am being asked to report into a colleague on an equivalent grade which I am unhappy about for a number of reasons. There is an unhealthy focus within the business on the role my equivalent has (i.e it is favoured) and i am concerned that a 'temporary' situation will become a permanent approach once the new manager is appointed.

Just looking for some basic advice on how to deal with this situation. I have already voiced my concerns but any practical advice on how to challenge this issue constructively would be VERY welcome.

Thanks!