Strictly Orthodox rabbis in London have set up a hotline to report any breaches of decency among the ranks of the community.
Notices have gone up in synagogues in Yiddish and English advertising a mobile number on behalf of the new Va’ad L’Toihar Hamachneh, Committee for the Purity of the Camp.
Locals can report any "suspicious" person or place which they believe has "breached the walls" of modesty and holiness.
A spokesman for the Union of Orthodox Hebrew Congregations said that the committee was not a UOHC initiative as such, but had been launched by a number of its rabbis in response to “public demand”.
But he made clear that there would not be any “modesty patrols”, as there were in Israel, which try to enforce dress standards on the streets.
The notice says that calls will be treated confidentially and the committee will "follow up and will investigate and do its best to solve the problem, according to guidance of the rabbis".