PARIS — Two Loral shareholders are seeking to block the company’s proposed sale of $300 million in preferred stock to Loral’s principal owner, saying the transaction is a “sweetheart deal” negotiated with insider information not available to other potential buyers.

In a letter sent Oct. 25 to the board of directors of New York-based Loral Space and Communications Inc., shareholder Murray Capital Management Inc. of New York backs many of the criticisms leveled a day earlier by Highland Capital of Dallas.

Murray and Highland Capital are pressuring the board to scrap its agreement to sell $300 million in preferred stock to MHR Fund Management LLC, which owns 36 percent of Loral’s common stock and three of eight seats on the board . If the transaction closes, MHR will have a fourth seat on the board.

In an apparent response to the complaint from Murray and Highland Capital, Loral announced Oct. 27 that it has asked MHR “to consider offering an alternative” to the proposed $300 million equity financing that would include “all interested shareholders.”

Murray and Highland say the Loral-MHR deal was crafted to benefit MHR, not Loral’s shareholders, and that ultimately it will give MHR full control of the company and a possible means of vetoing a future sale of Loral.

Loral spokesman John McCarthy said the company would have no comment on the shareholder protests. In an Oct. 17 announcement, Loral said the MHR preferred-stock sale was approved by “independent directors” and “disinterested members of the Loral board.”

Murray and Highland dispute this. Marti P. Murray, president of Murray Capital, says in his Oct. 25 letter that Loral’s board is already stacked in favor of MHR. In addition to MHR’s three selected members — including MHR founder Mark H. Rachesky — the board includes Loral managers, a Loral consultant and others whose relationship to MHR casts doubt on their independence, the letter says .

“With all due respect, upon close examination, it would seem almost impossible that any such ‘independent’ committee of your eight-person board could exist,” Murray says in his letter.

The Highland and Murray protests also question the terms of the Loral-MHR transaction, saying Loral’s recent turnaround nearly a year after emerging from Chapter 11 bankruptcy has increased the company’s value but is not reflected in the preferred-stock conversion price.

Murray says in his letter that he contacted Loral management after the MHR preferred-stock announcement and learned that “there is currently no specific transaction agreed to for which Loral would need $300 million in financing.”

The Highland and Murray protests reflect a view that Loral, after having spent several years in bad shape, is poised to deliver a payoff to shareholders in one way or another — a sale of its satellite manufacturing or satellite-services division, a purchase of another satellite operator, or internal growth as it develops the business.

“Now that we may be on the cusp of a bright future, we find the board entering into a transaction that will effectively snatch a great deal of our upside away from us and deliver it to MHR,” the Murray letter says.