Side-note: This is subtly different from other similar questions already on the site, so please read before marking as duplicate.
I applied for 2 jobs at the same time -- let's call them Initech and ACME for the purposes of this question.
Initech moved very fast through the interview/offer process, making me an offer on Tuesday of this week. When they made me an offer, I didn't say anything like "I accept the offer" on the phone, instead saying "Great" (which one could read as an implicit acceptance of the offer if one chose to).
(This was probably my first mistake -- I probably should have said that I currently had a few offers on the table, and I would review their contract and let me know when I have made a decision.)
Meanwhile, I had already had 1 interview and online test with ACME, and had decided I would prefer to work for there. After the online test, the recruitment department had moved a lot slower at ACME.
After getting the verbal/email offer from Initech on Tuesday, I contacted ACME and asked them to accelerate their process as I have a contract "on the table" but I would prefer to work at ACME. They scheduled a 2nd (and final) interview with me on Wednesday, which I had.
Shortly after the interview with ACME, the recruiter from Initech called me to ask me when I was coming in to sign the contract. I tried to stall it until Monday, but they were very keen to finalise everything (understandably, considering I did have this mistress job off to the side). I managed to defer the signing of the contract until Friday afternoon.
Just now (Thursday afternoon) I spoke to the recruiter from ACME and they have given me a verbal offer.
I'm now in a position where I need to get back to Initech and turn down their offer which I implicitly (to them, atleast) accepted. I wanted to know about the best way to do this -- I was definitely planning on doing it on the phone (after all, that's how the original offer was presented to me) as this is more professional and email seems like taking the easy way out.
I feel really bad that I wasn't up-front about the multiple offers from the start, but I made my decision at the time not to mention this and now I have to live with it.
What's the best way to renege my implicit verbal offer with Initech without burning any bridges and leaving a sour taste in their mouths?