This previous post of mine discusses "Bagsie" or "Bags I" as equivalent to "dibs." Also see some following posts

Okay I'm an Australian teenager and can help you here!
'Bagging' someone (NEVER 'bagging out') is just taking the piss out of someone. In the typical Aussie way, you'd hear it more among friends having fun than used when actually trying to be mean. I'd probably say it most about someones clothes or something. An example - If I just bought some amazing heels which I love and my friends all hate. So they're all laughing at them and saying 'I can't believe you paid money for those' and I'm like 'hey shut up, don't bag my shoes'.
'Bags' is also used here as an alternative to 'shotgun' or 'dibs' (or it was when I was a kid, now we say 'shotgun' more)
Edited by: nomad91

Thanks for all replies. You people are great!
The next time when someone (an Australian) say "Stop bagging me", I will ask him/her to clarify whether he/she was taking what I was dissin' seriously or light heartedly.
That's the problem with using slangs, we are not sure whether it should be taken light heartedly or maybe the person was not articulate enough to use another word like criticise or mock.
diss (from http://www.urbandictionary.com/define.php?term=diss)
Verb. Slang word that came from, and therefore shares the same definition as "to disrepect".
To lack respect.
Stop dissin' me or I'll kick your ass!

Nyamuk, if someone is saying to you "stop bagging me" they are taking your critisim seriously unless they are a very good friend who is saying this to you in a light or laughing way.
I do not know what the context is that this has been said to you. Perhaps someone has not been working as hard as they should and you have asked them to do things in a different way. You may have given them some feedback. This may have been perfectly OK. They may have felt they have been bagged. My point is that sometimes you might have bagged someone but it might be justified in the context.. however if you are trying to joke with someone rather than "diss" them or "have a go" (as we might also say in Australian) then they have recieved the wrong message.