New York  - Pfizer faces a shareholder lawsuit over its takeover of multi-billion dollar rival Wyeth, with the smaller firm's stockholders alleging the deal undervalues the company, Bloomberg financial news reported Friday.

The world's largest pharmaceuticals maker Pfizer Inc announced Monday that it would purchase Wyeth in a deal worth 68 billion dollars.

The suit filed by Wyeth shareholders in a Newark, New Jersey court on Tuesday alleges the firm's directors breached their duty by not getting a better price.

It would be one of the biggest takeovers in years and the most important one since the outbreak of the financial crisis. The last deal of comparable size was the AT&T-BellSouth merger for 70 billion dollars in March 2006.

Combined, the two companies have sales of around 75 billion dollars and profits of around 13 billion dollars. The merger will create the world's largest biopharmaceuticals company. Jeffrey Kindler, chairman and chief executive officer of Pfizer, will retain the top spot in the merged company. (dpa)