An Interstate Commerce Commission panel yesterday cleared the way for the nation's bus companies to raise fares by 6 per cent starting Friday and by an additional 7 per cent on May 15 in response to an industry request for an "emergency" rate increase.

However, the Justice Department immediately filed an appeal of the decision and asked the full commission to suspend the fare boost for at least two months.

The ICC is expected to take up the case today or Thursday in response to the Justice Department appeal.

According to the bus industry, which sought the higher fares about a month ago, profits have been falling sharply since 1972. Operating revenues were up 4.7 per cent for the major bus lines last year, but profits fell from $42 million in 1975, to $34 million the National Association of Motor Bus Owners said.

Officials of bus lines told members of the ICC earlier this year that money is needed to replace old buses, to maintain terminals and to pay for higher fuel bills.

If yesterday's decision is upheld by the full agency, the higher fares will take effect at midnight Thursday. For travelers on Greyhound Lines between Washington and New York, regular one-way fares will be boosted from $17.15 today to $18.20, and round-trip fares will be increased from $32.60 to $34.55. The one-way Washington-Baltimore fare would increase from $3.45 to $3.65.

In seeking a delay, The Justice Department told the ICC that no evidence of emergency conditions had been provided by the bus owners.

Noting that intercity buses are an important mode of transportation for poor, elderly and young people, the Justice Department said a so-called "emergency" fare boost cannot be permitted simply because some bus firms say they may be unprofitable. Companies accounting for more than 84 per cent of intercity revenues operated at a profit last year, Justice said.

According to the Justice Department, the intercity bus industry filed 10 fare increase proposals totaling 63 per cent from 1969 to 1976. In the last three years alone, across-the-board fare boosts of 35 per cent have been approved by the ICC "with only minimal delays," Justice stated.

Intercity bus travel is dominated by Greyhound and Continental Trailways, a unit of Holiday Inns. Together, these two firms accounted for 90 per cent of national revenues. Greyhound's profits have been declining, and 3 of Trailways' 15 component companies reported losses in 1976.