WASHINGTON – Senators working on a sweeping immigration bill will likely abandon the idea of a new high-tech ID card for workers because it’s too expensive, a key negotiator said.

That means their emerging legislation, which they’ve promised will crack down on employers who hire illegal immigrants, likely will seek to expand a little-used system criticized as error-prone and vulnerable to fraud that employers can use to check the legal status of workers, mainly using Social Security numbers.

The system, called E-Verify, is now voluntary, and officials with labor and immigrants’ rights groups say it would have to be greatly improved before being required nationally.