A judge approved a class-action lawsuit against Wal-Mart Stores Inc. (WMT) by employees in Pennsylvania who say the company pressured them to work off the clock, claims that mirror those in suits filed around the country.

A California jury last month awarded Wal-Mart workers $172 million for illegally denied lunch breaks, while Wal-Mart settled a similar Colorado case for $50 million.

In Pennsylvania, the lead plaintiff's suit alleges she worked through breaks and after quitting time — eight to 12 unpaid hours a month, on average — to meet work demands.

"One of Wal-Mart's undisclosed secrets for its profitability is its creation and implementation of a system that encourages off-the-clock work for its hourly employees, ..." Dolores Hummel, who worked at a Sam's Club in Reading from 1992-2002, charged in her suit.

The suit was approved for class certification late last month by Philadelphia Common Pleas Court Mark I. Bernstein. The class could include nearly 150,000 current or former employees who worked at a Wal-Mart or Sam's Club in the state since March 19, 1998.

"We strongly deny the allegations in this lawsuit. Wal-Mart's policy is to pay associates for every minute they work," the Bentonville, Ark.-based retailer said in a statement.

Wal-Mart earned $10 billion in 2004.

The class-certification decision followed days of hearings that examined Wal-Mart's pay records, break policies and even electronic systems that show when employees are signed on to cash registers or other machines, said plaintiff's lawyer Michael Donovan.

"There's a lot of electronic evidence, that when you examine it shows that these people aren't getting breaks, but they're continuing to run the cash register or do inventory or whatever," Donovan said.

Wal-Mart, which is appealing the California verdict, may also pursue an appeal of the class-action certification in Philadelphia, according to lawyer Martin D'Urso.

The certification alone does not prove any wrongdoing, the company's statement noted.

The suit was initially filed in 2002. At the time, Wal-Mart employed more than 31,600 people in 123 stores in Pennsylvania, the suit said.

Hummel had to work off the books to meet quotas on cakes she made in the bakery, Donovan said. She was eventually dismissed over her productivity level, he said.

The California jury award — which includes $115 million in punitive damages — covers about 115,000 class members. That suit involved unpaid lunch breaks.

Hummel's suit cites a Wal-Mart corporate policy that gives hourly employees one paid 15-minute break during a shift of at least 3 hours and two such breaks, plus an unpaid 30-minute meal break, on a shift of at least 6 hours.

The company's break policies can vary according to state law, spokesman Kevin Thornton said.

According to Donovan, similar suits against Wal-Mart have been granted class certification in states including Massachusetts and Minnesota, but denied in New Jersey.

Shares of Wal-Mart rose 24 cents, or 2.4 percent, to close at $10.41in trading on the New York Stock Exchange.