WASHINGTON — The IRS is resuming the use of private debt collectors amid a wave of telephone scams in which fake government agents tell innocent taxpayers to pay up or face jail, the tax agency announced Tuesday.

The IRS stopped using private debt collectors in 2009 after the agency determined that IRS employees could better do the work. But Congress passed a law in 2015 requiring the IRS to restart the program.

The IRS says it will soon start turning over the accounts of 100 taxpayers a week to four private debt collectors. The program will grow to 1,000 accounts a week for each firm by the end of summer.

The firms can keep up to 25 percent of what they collect.