Can maid of honour call uninvited guests?

I am the maid of honour at my friend’s wedding. She has asked me to call people who have added uninvited guests to their RSVP response card and tell them they can’t bring their uninvited guests. Is this one of the responsibilities of the maid of honour?

No, it isn’t stated anywhere that a maid of honour’s responsibility is to call guests to let them know that they have uninvited guests on their RSVP. Now, having said that, the maid of honour is responsible for being the bride’s “go to” person, the one the bride will lean on especially in trying times.
It may be that the bride is uncomfortable calling these guests and informing them that they cannot bring another person with them and as a result, has asked you to do so. The bride may feel that this will be easier since she is more removed from actually having to say “No” herself (especially if she worries that she may end up saying ‘yes’ and thus, blowing her budget on the wedding). At the same time, this may also put you in an awkward position since you will now be making those phone calls.

My suggestion is to have a list of handy replies ready for when you make the phone calls. That way, you will not be caught off guard or feel awkward about making those calls yourself. Here is an example:

“Hi ______, I’m Amy, Jane’s maid of honor. I’d like to thank you on behalf of the engaged couple for your RSVP, which we received today. Jane and Ben have requested a very small wedding with only close family and friends. They’re excited about seeing you at their wedding and apologize for not being able to accommodate your guest….”