BERLIN (AP) _ British authorities in West Berlin have installed ladders along the bank of a river where East Germans have tried to swim to the West, a British spokesman said today.

Diplomatic spokeswoman Biddy Brett Rooks said the ladders, which are like those used in swimming pools, were installed ''for humanitarian reasons.'' However, she declined to say they were specifically aimed at helping escaping East Germans climb out of the water.

''Our purpose is to help anyone in the water, however they got there,'' the spokeswoman said.

The ladders and a stretch of rope were placed last week on the western bank of the Spree River in the British sector of West Berlin, she said. Communist East Berlin lies on the other side of the river.

During one dramatic escape attempt in February, Martin Notev was grabbed by East German border guards in a patrol boat after he had touched the western bank of the Spree.

Britain, the United States, and France protested, saying the 21-year-old East German man had already reached the West although he was still in the water.

Notev was sentenced to prison, but East Germany reversed itself and freed him after the Western protests. He was sent to West Berlin on June 21.

Berlin was split into sectors controlled by Western allies and the Soviet Union at the end of World War II. The East built the fortified Berlin Wall in 1961 in an effort to prevent East Germans from escaping.