New York - Amgen Inc, the worlds largest biotechnology company, is being sued by 15 US states after an investigation into an alleged nationwide kickback scheme that aimed to boost sales, New York's attorney general said Friday.

Andrew Cuomo, the attorney general, said Amgen and two units of AmerisourceBergen Corp offered kickbacks to physicians and others to increase sales of the anaemia medicine, Aranesp.

The complaint charges that the companies gave free samples of Aranesp to medical providers such as physicians, then encouraged them to bill insurance companies and the government's Medicaid programme for reimbursement.

"Drugs should be prescribed to patients on the basis of need, effectiveness and safety, not on a corporate giants promise of an all-expense paid vacation," Cuomo said.

Aranesp was Amgens third-biggest drug in 2008 with 3.1 billion dollars in sales, according to data compiled by Bloomberg from company releases.

We believe that the allegations are without merit, and we look forward to the opportunity to examine these matters with the states before the court," David Polk, an Amgen spokesman, told Bloomberg in an e-mail. (dpa)