As it had predicted last month, Great Atlantic & Pacific Tea Co. today reported a fiscal third quarter net loss of just over $5 million.

The major supermarket chain said it had a loss of $5.022 million on sales of $1.31 billion in the quarter ended Nov. 26. A year before, A&P reported virtually identical sales but had a net profit of $5.085 million, or 20 cents a share.

For the first nine months, A&P reported a profit of $2.92 million, or 12 cents a share, against $22.07 million, or 89 cents a share, a year before. Nine-month sales totaled $5.42 billion, against $5.33 billion the year before.

The Montvale, N J based A&P said its third quarter results represent a loss of $2.382 million from operations from estimated losses of $264 million from the closing of stores and other facets of its redevelopment program. A&P said it had 1,917 stores operating at the end of its third quarter, compared with 2,077 a year before.

A&P, the second largest U.S. grocery chain, said its 1976 quarterly earnings and its nine-month earnings for both years reflect use of the company's tax-loss carryforward. For the year-ago quarter, the tax credit was $2 million and for the latest nine months it was $1.4 million. For the year-ago nine months, the credit totaled $9 million.

Chairman Jonathan Scott, who has presided over a drastic paring of A&P's older inner city stores, said the third quarter loss reflected rising costs, especially for labor, which were not offset by higher sales.

Revenues for the quarter were flat - $1.81 billion for 1977 and 1976 - and rose only 1 per cent for the nine months.