NEW YORK - A Merck & Co. sales representative is suing the drugmaker for at least $100 million, saying it does not give women equal opportunities for advancement and punishes employees for maternity leave.

Kelli Smith, who has worked at Merck since 2004, says in the lawsuit that the company's sales plans create incentives to discriminate against women, that women are discouraged from advancing their careers and are told they have to choose between being mothers and taking bigger roles at the company, and that men get more opportunities to meet senior managers and develop important contacts. She said the company retaliated against her for drawing attention to the issues.

She wants to create a class-action lawsuit on behalf of female sales representatives who have worked at Merck since October 2009.

Merck confirmed Thursday that it was being sued. It said the lawsuit lacked merit and the company would defend itself. The company said it had a strong antidiscrimination policy and was committed to providing equal opportunities to all of its employees. The company said its policy also prohibited retaliation against employees who brought complaints.

Smith, a sales representative in Toms River, N.J., says that she has won awards for her work but that she was unfairly demoted after taking maternity leave in 2010, and was told by her team leader that she had been demoted because of the timing of her leave.

She said she was told she was ineligible for a prestigious company award for the same reason. She says every other member of her team received that award in 2011 except a female employee with children and a man who had just joined the company.

The lawsuit also says the company discourages the hiring and promotion of women because compensation for managers and directors is decreased when employees take legally protected leave.

Merck is based in Whitehouse Station, N.J.