THE HAGUE, Netherlands (AP) _ The European Economic Community will step up its legal actions to end competition-stifling restrictive accords among European airlines, EEC Competition Commissioner Peter Sutherland said Friday.

''You can expect to see a reinforcement of our action between now and the end of the year,'' he told a meeting of EEC chambers of commerce here. He did not elaborate.

In July, the Commission gave national air carriers until Sept. 14 to indicate how they will end their restrictive agreements. Sutherland said some accords have been ''abandoned or modified,'' but added, ''much remains to be done.''

The Commission began legal action against 10 national air carriers in 1986 and against three more in July.

In the absence of an EEC-wide airline deregulation agreement, the Commission wants an end to price-fixing and capacity-sharing deals that stifle competition and keep costs and fares high.

The EEC deregulation talks collapsed in June in a dispute between Britain and Spain over the Gibraltar airport.

Sutherland said Europe's airline industry was a ''bastion of protectionism. It is difficult to identify other sectors where a comparable degree of protectionism has been permitted to reign unchallenged for so long.''

The airlines affected by the EEC's legal proceedings, initiated under the EEC's fair competition rules, are:

Aer Lingus (Ireland), Air France, Alitalia, British Airways, British Caledonian, KLM Royal Dutch Airlines, Lufthansa (West Germany), Olympic Airways (Greece), Sabena (Belgium), Scandinavian Airlines System, Iberia (Spain), Luxair (Luxembourg) and TAP (Portugal).