Asset manager Energy Income Partners LLC, one of the top shareholders in Magellan Midstream Partners, said on June 8 that it intends to vote against pipeline operator ONEOK Inc's deal to buy Magellan.

Energy Income said in a letter addressed to the company's board that the taxes paid by its funds and investors will exceed the premium offered by ONEOK and any potential benefits from the merger.

Energy Income is the fourth largest shareholder in Magellan with a roughly 3% stake.

The asset manager also said it wants Magellan to remain a stand-alone entity whose returns on invested capital are far superior to ONEOK.

ONEOK said last month that it would acquire Magellan in a cash-and-stock deal valued at about $18.8 billion.

Magellan and ONEOK did not immediately respond to requests for comment.