The Pennsylvania Attorney General's Office filed a sweeping lawsuit Wednesday against a big nursing home chain, accusing it of understaffing that has left residents "thirsty, hungry, dirty, and unkempt."

The lawsuit is the first to stem from the office's controversial practice of hiring an outside law firm to dig into the quality of care at nursing homes.

The suit against the Golden Living chain, with 36 facilities in Pennsylvania, was developed with the help of the Cohen, Milstein, Sellers & Toll law firm in Washington. The firm will keep 21 percent of any fines paid by the chain.

In a statement later Wednesday, Golden Living said the suit was "baseless and wholly without merit."

The firm also criticized Attorney General Kathleen G. Kane, saying she has an "inappropriate and questionable relationship" with Cohen Milstein, which it said "preys on legitimate businesses and is then paid by contingency fees."

The suit says Golden Living was guilty of deceptive advertising in Pennsylvania in that it promised decent care but did not deliver it. In fact, it says, residents found "no one was available to meet their most basic needs, like escorting them to the toilet or refilling a water glass."

The suit cites interviews with former staff and family members of residents as well as critical reports from the state Department of Health to raise questions about conditions at about a third of the chain's homes.

It mentions interviews with 16 unnamed ex-employees and three unidentified family members to say that residents were denied proper baths, left in soiled clothes and bedding, and sat hungry because no staff was there to assist them with dining, among other abuses.

With headquarters in Arkansas and Texas, Golden Living is the nation's third-largest nursing chain, trailing Genesis HealthCare Corp. and HCR ManorCare. It has homes in 21 states.

In Pennsylvania, its homes include facilities at 7310 Stenton Ave. in Philadelphia, 25 W. Fifth St. in Lansdale, and 833 S. Main St. in Phoenixville.

The suit cited information from three former workers as well as regulatory records to criticize care at the nursing home on Stenton. The informant with the most recent employment history last worked there in 2012.

One ex-worker said a lack of staff meant that residents stayed in nightclothes well into the day. Another said staff shortages meant that residents developed pressure sores and that incontinent residents would wait hours for a change of clothes. The third "confidential witness" said the place was often short on routine supplies such as shampoo, washcloths, and diapers.

In April, a lawyer for several nursing homes struck first against the Attorney General's Office, filing a lawsuit seeking to void its contract with Cohen Milstein. The homes' suit said the attorney general was illegally usurping the role of the state Health Department and facilitating a drive by Cohen Milstein to "create a 'problem' where none exists in a search for profits for itself."