Giving the bottle ebm top ups to dd from pretty much day one made no difference to her willingness to bf in our case - she continued to wholeheartedly prefer boob to bottle, and continued to bf up till just shy of two.
Am sure there must be some evidence to say it can potentially cause problems in a small number of cases, but think it is nonetheless helpful for mums wanting to bf not to feel that introducing a bottle, if they need to, must be the death-knell for the nursing relationship. Because for us, it made fuck all difference!
Indeed, anecdotally, I have an overwhelming amount of examples of babies who took the bottle in their early weeks (because needed to top up, because baby couldn't latch, because baby was prem, because mum had pnd, because whatever whatever whatever) but nursing relationship continued, throve, and in fact the babies became lovely little boob-demanding-monsters!
Sorry, perhaps I sound a bit emotional about this - I was looking back at some texts I sent to my friends when I was told by the HVs I needed to bottle feed ebm to dd - I clearly basically believed, then, that I would no longer be able to bf dd because she'd prefer the bottle, and therefore felt fucking miserable and upset. When there was, in fact, no reason for me to feel like this at all.
If there is some statistical evidence for the nipple confusion thing, then perhaps it's appropriate to cite it, but even then only in a way which is still respectful, supportive and encouraging to women who feel they have no other choice to make.