Before you go out with your dress clinging to your tights and creeping up your backside, let me share with you some ideas on how to handle this. First, static cling, is a build-up of an electrical charge, often from polyester dried in the dryer. There are several quick tricks to get rid of it.
The fastest, when you're trying to get out of the house, is to spray your backside with Static Guard - I've been known to keep a can at the office to save all the innocent neophytes who don't know. It stinks, but it works.
If you can't get to that, hand lotion, smeared all over the fabric will often do the trick. If you could still find hairspray, it will work too.
A dryer sheet will work -- rub all over the area. Dryer sheets are essentially wax embedded into the sheet.
You could try touching grounded metal and the shock may get rid of it.
And lastly, don't dry your polyester in the dryer - that's where static gets built up.
Using fabric softener - even white vinegar as the softener - will help.
Get prepared for winter right now - and you won't be the girl with the dress creeping up her tights having a cringeworthy moment!