Can I still bid against the consortium if I am a member?

Yes, but you would need to declare your intentions to the consortium and you could not be party to consortium discussions on price and other commercially sensitive information.  These sorts of ‘rules of engagement’ issues will be covered in the consortium’s partnership agreement (see point above).

Of course, the merits and advantages of not bidding against the consortium, but instead being part of a consortium bid, will be actively promoted.