BERLIN — A government study released Thursday supports what many German consumers have long suspected: Internet broadband service is much slower than advertised.

The study by the German telecommunications regulator, the Bundesnetzagentur, measured the Internet connection speeds of 250,000 consumers from June through December last year, making it one of the largest reviews of broadband service anywhere.

The results showed that only 15.7 percent of those using fixed telephone lines and 21 percent using mobile devices achieved the advertised maximum speeds.

Nearly half of German consumers using the supposedly fastest wireless broadband networks, which run Long Term Evolution technology, received Internet service at speeds that were no more than half as fast as the advertised maximum, the regulator found.