Trusthouse Forte, a London-based food and lodging company, will operate a large new luxury hotel planned at the Gallery Place complex at Seventh and G Streets NW, it was announced yesterday.

The world's largest hotelier, Trusthouse Forte had tried earlier to enter the Washington market but had been unsuccessful until now.

The $150 million, 704-room hotel will be named the Washington Excelsior at Gallery Place. Construction, scheduled to begin in May, is to be completed by the fall of 1984.

The new luxury facility will have three restaurants, two lobby lounges, recreation facilities, shops, and an enclosed parking garage that will accommodate 1,100 cars. It also will have direct access to the Gallery Place Metro stop.

The 12-story Gallery Place hotel, retail, apartment and office complex is a major urban renewal project for the rundown Seventh Street corridor, to be built on a block of land bought from the city under an agreement completed in August.

Capital Landmark Associates Inc., a minority-controlled partnership, developer of the complex, yesterday announced its agreement with Trusthouse Forte to build the hotel.

The hotel is to occupy the ground floor and upper six floors of the 12-story building, the announcement stated. It also will have a number of meeting and banquet facilities and a ballroom that will hold up to 1,400.

The Gallery Place project is just one of at least 20 new hotels being built or planned in the District. A recent Washington Post census found that the number of hotel rooms in Washington could jump by 50 percent to more than 24,000 in the next four years if all these planned facilities are built.

Trusthouse Forte operates more than 800 hotels throughout the world and plans substantial expansion of its operations in the United States in the next year.

Its current operations include the Westbury in New York City, Plaza of the Americas in Dallas and the Plaza Hotel in Philadelphia. The company also has hotels under construction in Little Rock and Tulsa and said it plans to develop facilities in 17 other North American cities by the end of 1982.

"We are pleased to have a company with the worldwide reputation of Trusthouse Forte to join us in building what will be one of Washington's geat hotels," said William Fitzgerald, president of Capital Landmark, in a statement.

The architect on the project is Vlastimil Koubek, who designed L'Enfant East and West and Judiciary Plaza buildings as well as hotels in Crystal City and Washington, the developers said.

The financial package was arranged by Walker & Dunlop Inc.,