BONN, West Germany (AP) _ The Berlin Wall is ''painful evidence of the inner weakness and insecurity'' of Communist rule in East Germany, a West German Cabinet minister said Monday on the eve of the 24th anniversary of the wall's construction.

''Because it cannot tolerate competition with a free and democratic society, (East Germany) must preserve itself by fencing in its people, in order not to lose them,'' said Heinrich Windelen, inter-German relations minister.

Communist authorities started building the wall on Aug. 13, 1961, to stop illegal emigration to the West through West Berlin, the part of the divided city protected by U.S., British and French troops since 1945. Berlin is 110 miles inside East Germany.

''The wall separates in painful ways people in the largest German city,'' said Windelen. ''It cuts an economic unit unnaturally in two and has dismembered one of Europe's most significant cultural centers.

''As long as the East German government reckons that it cannot renounce the wall and other blockade measures (along the inner-German border), it will have to cope with the damaging consequences to its international image,'' he said.

Hans Buechler, an opposition Social Democratic deputy in the West German parliament, cautioned against ''ideological phrase-mongering'' on the anniversary.

East German living standards have improved considerably in the past 15 years, weakening the lure of West Germany for East Germans, said Buechler.

The state-run East German news agency, ADN, carried no reports Monday on the anniversary.

A West Berlin-based watchdog group released its annual report on conditions along the border between the two Germanys, saying the number of East German escapes continue to decline as Communist border barriers are ''perfected.''

The report by the Working Group August 13, named after the date of the wall's construction, said 312,393 East Germans had emigrated legally since it was built, and 38,920 had escaped over Communist walls or fences along the 854-mile frontier between the Germanys since August 1961.

Escapes have dwindled from thousands annually in the early 1960s to less than 200 a year, said the group, which uses figures from official sources.

It said 67 East Germans had escaped this year.

At a West Berlin news conference held by the group, five former East German border guards who escaped over the Berlin Wall said Communist sentries are still under ''shoot-to-kill'' orders in an escape situation.

Former guard Georg-Stephan Schmutzenhofer, 18, said soldiers are taught that every escapee is an enemy of East Germany and must be ''eliminated.' ' Schmutzenhofer scaled the wall despite gunfire from fellow sentries.