As Walgreen, the big drugstore chain, considers a deal that would allow it to reincorporate abroad, many shareholders are elated, saying it could save millions of dollars a year on taxes.

But at least one Walgreen investor wants the company to remain in the United States. The CtW Investment Group, which owns less than 1 percent of Walgreen’s shares, sent a letter Tuesday to the company’s management, making the case against such a transaction.

“Redomiciling overseas would likely be detrimental to the interests and rights of long-term shareholders, heralding a step backward in the company’s corporate governance,” Dieter Waizenegger, the chief executive of CtW, wrote in the letter, which was sent to James Skinner, Walgreen’s chairman.

The transaction that Walgreen is considering is known as an inversion, in which a U.S. company acquires a foreign competitor and reincorporates in a low-tax country. Companies then often pay lower rates on earnings generated outside the United States and can raise cash overseas more easily.

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Inversions are increasingly popular with companies and investors, and the pace of such deals has picked up in recent years. Pfizer, the big drugmaker, recently became the largest and best-known company to attempt such a move with its proposed acquisition of AstraZeneca.

Walgreen could be next. At a meeting in Paris last month, some Walgreen shareholders pressed management to consider such a move. Walgreen is in the middle of a two-part acquisition of Alliance Boots, the British drugstore chain, and could structure the deal to allow it to invert.

But despite support for the plan by some big Walgreen shareholders, CtW, which advises union pension funds, says such a move would be a mistake despite the potential tax savings.

Walgreen declined to comment.

If Walgreen reincorporated in Switzerland, where Alliance Boots is based, the influence of shareholders could be diminished, CtW said. Swiss law gives shareholders less protection, CtW said, making it harder for investors to seek remedies through courts in the event of fraud or a dereliction of board duties.

CtW also said it was wise to be sensitive to the brewing political debate about inversions. In recent months, several senators and President Obama have proposed legislation that would curtail the practice. And while no new laws are yet in place, there is a belief on Wall Street that the window for such deals could close soon.