Yeshiva World reports (via Ynet) that a Tznius Hashgocho (modesty certification) has been established in Israel. A Tznius Beis Din (court) will give certifications to worthy vendors. One particular target of this seems to be Lycra.
Now, I'll certainly entertain arguments that some frum women dress provocatively. We have some Hot Chanies who live in my own neighborhood. But the idea that you can fix the problem with a hashgocho is downright silly.
As eliezer notes in the comments on the YW thread:
What’s to stop a women from going into to one of these stores and buying a dress two sizes too small? How can that be stopped? What if a dress looks tight, but a very thin woman buys it and it fits her Tzniusdikly?
There are just too many variables that go into determining whether a particular outfit is proper for the wearer. Size, material, color, body style, fabric and probably a dozen other factors go into it. This isn't a decision that can be made on a store-by-store basis.
Furthermore, what will be with stores that sell lingerie? How will they judge which stores get a hashgocho when all the clothing therein is meant to be worn in the privacy of one's own home?
In any event, the concept lacks two important factors that are necessary to make it work - an enforcement mechanism or the willingness of the public to only buy items with the hashgocho.
The former is illustrated by drugs. In order to buy a drug in the United States, it must be approved by the FDA. If it is not approved, it cannot be (legally) sold in the US and stores that sell it (and people who buy it) can face criminal charges.
The latter is illustrated by food hechshers. No one is going to put you in jail if you buy non-kosher food. But since most Orthodox Jews voluntarily keep the laws of kashrus, the system works.
This system has neither element. There is no enforcement mechanism and there is no public will (by virtue of the fact that the clothing is already being bought and worn). Even if you closed down every clothing store that lacked a hashgocho in the cities where these people live you could not enforce the decree. Now that we live in the days of easy travel, catalog shopping and the Internet, you can order things from around the globe and well out of reach of the Tznius Beis Din. As such, the edict is, to all extents and purposes, unenforceable. And an unenforceable decree is worse than no decree.