In business situations, is it acceptable to introduce a business partner as simply "my partner" or is it necessary to specify "my business partner"? I have seen both used and the issue seems to revolve around ambiguity surrounding the increasing use of "partner" to allude to a romantic connection. Does it matter if my partner is of the same or opposite sex?
'Acceptable' to whom? The majority of English users know that partner is sometimes used for a business partner and sometimes for a romantic partner. If the word's used in a business context, it's not likely to be misunderstood; if you go for a drink after work and need an introduction to an acquaintance, it would be polite to say 'business partner'to avoid confusion. But there's no rule that says "after 6 p.m. the word means romantic partner"; everything (and particularly Does it matter if my partner is of the same or opposite sex?) depends on your acquantainces.
I worked for two women who owned a business together who referred to each other as "my partner", as in business partner. In our liberal open-minded town, where unmarried people of all orientations would introduce a significant other as "my partner", occasionally people would instantly assume they were also a lesbian couple. Then one of them would mention her husband and the person assuming the women were also romantic partners would be a bit embarrassed. My bosses got a laugh out of it, no harm done.
I think having to specify "business partner" to avoid confusion would depend on the context but that in most situations just "partner" should suffice as it is perfectly acceptable English. One shouldn't have to go to the trouble to be very specific in the wording in order to pre-empt any assumptions on the part of the listener, whether the are negative, positive, or neutral assumptions. In some circles, such as in the aforementioned liberal town, going to the trouble to specify "business partner" with a person of the same sex might in fact be seen negatively, if the listener was predisposed to thinking the clarification sounded homophobic.
It is completely acceptable in a business context to talk simply of 'my partner' without giving rise to confusion. However, with changing times and wider use of the phrase, I can foresee the possibility of just the distinction that you are querying. 'Partner' has the specific legal meaning of a person jointly and severally liable for the other's debts when used in a business setting but carries no such connotation in romantic situations!
I feel, therefore, that there may well be times when use of phrase 'my business partner' might serve to clarify the relationship.