Mistakenly only thought to refer to Geordie lingo, but has been used by MackemsSunderland for just as long but in a slightly different context.
Imagine the most extreme possible sarcastic meaning of the phrase 'As if' and 'Of course' but with even more negation of authority, then you might touch the full extent of it's meaning.
1)Diplomat-"The war in Iraq was not motivated by oil."
North east England inhabitant-"Why Aye!"
2)"It is possible to find an uncorrupt politician"