After countless number of tries my solution was simply not use backBarButtonItem! As whatever i do it always goes to previous viewController instead of calling its selector
Instead I use only leftBarButtonItem for navigation, as it guarantees calling my action.
Here an example
UIButton *backButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 27, 22)];
[backButton setImage:[UIImage imageNamed:@"backbutton"] forState:UIControlStateNormal];
[backButton addTarget:self action:@selector(backButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backButton];
This certainly calls backButtonPressed action.. This works both for IOS 6 and 7