Canadian beverage chain DavidsTea has come under scrutiny in several U.S. states for its alleged use of "on-call" shifts to control labour costs.

Attorneys general in New York and eight other jurisdictions have sent letters to 15 retailers, including Montreal-based DavidsTea, seeking information about their use of the scheduling practice that requires employees to call before their shift to find out if they are required to work.

The letter requests information and documents about the company's use of the controversial scheduling practice.

DavidsTea didn't immediately respond to requests for comment.

New York Attorney General Eric Schneiderman said in a release that on-call shifts are unfair because unpredictable work schedules make it difficult to arrange reliable childcare or other pursuits while adding to stress and strain on family life.

Some U.S. states have call-in pay laws. New York state, for example, requires employers to pay at least four hours or the number of hours in the regularly scheduled shift if it less, at the minimum hourly wage.

Letters were also sent to American Eagle, Aeropostale, Payless, Disney, Coach, PacSun, Forever 21, Vans, Justice Just for Girls, BCBG Maxazria, Tilly's, Zumiez, Uniglo, and Carter's, many of which have operations in Canada.

Following a similar effort last year, several companies, including Abercrombie & Fitch, Gap, J.Crew, Urban Outfitters, Pier 1 Imports and the parent company of Bath & Body Works and Victoria's Secret ended the use of on-call shifts.