Some of the merchants believe his actions are motivated by the upcoming elections for the Jerusalem Rabbinate.
The "Shabbat Alert" group was founded about 20 years ago by Rabbi Bezalel Goldschmidt. Every Friday, a group of haredi yeshiva students would arrive at the market to ensure that the stands are closed before the start of the Jewish day of rest.
As reported by the Yedioth Jerusalem newspaper, in the past the group got into a verbal confrontation with customers and merchants, which led to physical violence.
The association supporting the "Shabbat Alert" activity was terminated about a month ago, but Rabbi Schlesinger decided to revive the initiative.
According to the rabbi, since Israel installed Standard Time several weeks ago, Shabbat begins earlier and therefore he must ensure that the market is shut down without any desecration of the Shabbat.
"We don't shout at the merchants, but rush them politely," he claimed. "Some say to me, 'Rabbi, give me a blessing,' and I promise to do so if they shut down, and it works.
"But I am very angry at religious and haredi Jews who start shopping at the market just before Shabbat, creating a serious obstacle," he added.
Some of the merchants, however, are unhappy with the "Shabbat Alert" group. According to one of them, the rabbi's activity stems from political considerations.
"He is creating public relations for his activity among the haredim by going to the seculars in order to promote himself," argued the merchant.
One store even posted a picture on its wall showing haredim in their Shabbat clothes pushing a business owner onto the wall on the background of the market stands.
Asked about the merchants' claims that his conduct is political, Rabbi Schlesinger said: "We do it out of love for Israel and not for any other reason but to honor the Sabbath."