A word of warning
The sequence of events is very important. Think carefully before doing anything. I know a little about contract law and so should you.
Many years ago, an uncle of mine got a fantastic job offer from a company. Thrilled, he gave notice at his existing job. Everything got into motion.
Two weeks later he got a letter from the new company saying that the offer to him had been withdrawn - they had found a better candidate. Immediately he went back to his old employers and asked for his job back. They refused saying they had formally accepted his resignation. He was left with no job and a family to support.
Moral of the story
Make sure you get a job offer in writing in contractual terms before giving your notice. Also formally accept the contractual offer in writing and make sure they have acknowledged your acceptance of the offer before handing in your notice at the old job.
Having given that warning, it is common for employees to use a job offer as a negotiating tool.
Suggested course of action (but I am not a lawyer so consult one before following my ideas)
Get a formal, written job offer from the new people.
Do not accept it yet.
Show the formal job offer to your current employers.
Ask them to provide a better offer (promotion) in writing, saying exactly what your new position/salary will be.
You now have two offers in writing. Each forms the basis of a possible contract. Decide which you want and formally accept that one. You must then receive formal written confirmation from the company you choose that they have received your acceptance.
Finally, formally decline the offer from the non-chosen job and, if it is the current one, give them your notice.
Everything should be in writing at every stage and the sequence of events is critical. To use contract law, get the following things in formal written/printed and signed documents.
- Job offer in writing
- Promotion offer in writing
- Accept 1 or 2 in writing.
- Get formal written acknowledgement of your acceptance.
NOW YOU HAVE A CONTRACT.
- Decline offer of party you don't want to be with. (Give notice if necessary)
I am not a lawyer nor an employment specialist. I am merely giving lay advice based on experience of a family member and a limited knowledge of contract law. You must use your own judgement, and obtain legal advice if necessary.