A House Government Operations investigative subcommittee has decided that the Rural Telephone Bank (RTB), another of those obscure federal creatures that is supposed to help the less fortunate, is acting instead like a rogue utility.

In a report released last week, the subcommittee on government information, justice and agriculture said the RTB has accumulated more than $179 million in "excess profits" that should have gone back to rural telephone users.

The bank was created by Congress in 1971 to help get more telephone service into rural areas by providing low-cost financing to country telephone systems. The bank was ordered to lend money at no more than its own cost of borrowing.

But Chairman Glenn English (D-Okla.) said hearings held earlier this year showed that, contrary to congressional intent, the bank had been "deliberately manipulating" interest rates in a way that made the operation "extraordinarily profitable."

The hearings and an investigative review of bank policies showed that "illegal profits" were accumulating at a rate of more than $20 million annually through "phantom borrowing, manipulated projections and rounding rates upward," English said.

As a result, he added, the higher interest rates meant that the bills of some rural telephone users were as much as $4 per month higher than they should have been.

Notwithstanding the findings, some Republican members of the committee thought they heard unwarranted political static on English's line. They agreed with most of the major points, but complained that "rhetoric" and "tone" in the report unfairly blamed the Reagan administration for the bank's behavior.

"Whatever culpability exists on the part of the bank . . . extends to the bank's board of directors. Six of the 13 members of the board are elected members who represent telephone operating systems -- the bank's borrowers," the GOP side said.

The minority also complained that if the RTB followed the letter of the 1971 law and loaned money only at actual cost "it could not even cover its administrative expenses" and would have to rely on subsidy from the Treasury.

English, who chuckled at the charge of partisanship, is liable to have the last word in this one. The House Agriculture Committee last week approved an English amendment to its budget reconciliation package that would require the RTB to observe the cost-of-money requirement.

The amendment would force the bank to recalculate past and future loan rates to reflect actual costs and it would set up a reserve of at least $77 million to help protect the RTB against interest-rate fluctuations in the future.

As for the excess profits, the Government Operations panel recommended that the bank's directors figure out a way to pay back the $179 million to rural telephone systems and to give Congress a return call with its decision by Feb. 1.