Communal leaders have condemned letters encouraging recipients to take part in "Punish a Muslim Day."
Chief Rabbi Ephraim Mirvis said the “horrific calls over recent days are a sobering reminder of the depravity of Islamophobia.
“The reaction of the Jewish community is unequivocal: threats of violence and prejudice directed at British Muslims undermine everything that it means to be British and are totally abhorrent.
“Today, as the Government issues its proposed strategy for better integration in our communities, which includes a range of important issues that they are consulting on, it particularly calls out the false and destructive narrative that being Muslim is incompatible with British values.
“This kind of campaign to terrorise and divide our society makes clear just how important it is for us to challenge that narrative wherever it is found.”
The Board of Deputies said the letters which were sent out in a number of UK cities, calling on people to verbally and physically attack Muslims, are sickening.
A spokesperson for the Board said: “We also note that potentially harmful substances and anti-Muslim letters have been sent to some Muslim MPs.
“Our community knows all too well how concerning it is to be on the receiving end of such threats.
“We will be writing to the MPs affected to express our sympathy and to make it clear that British Jews stand united with British Muslims in our opposition to racism and violence.”
Images of the A4 notes, contain a list of violent acts people should carry out against Muslims in their community on April 3.
Stella Creasy, Labour MP for Walthamstow, said she was helping constituents report antisemitic graffiti, when she found out that Muslim residents had received the letters.
"We have to do more than condemn these individual incidences," she said.
"We must in this House speak up for the communities we represent and the power of diversity and immigration to enrich all of our lives."
Reform's Senior Rabbi Laura Janner-Klausner also condemned the letters and sent a message of solidarity to the Muslim community.
This is utterly despicable and so scary. Our British Jewish community knows all too well what it is like being targeted as a minority group and it stands with all British Muslims who face this intimidation. https://t.co/l4yjRsUfuJ— APPG on British Jews (@APPGBritishJews) March 13, 2018
Rabbi Janner-Klausner praised the response of Ian Austin, Labour MP for Dudley, who said he would use the day to visit as many mosques and Muslim community centres in his constituency as possible.
She also reiterated a called on the government to adopt a clearer definition of Islamophobia in a similar way to how it has defined anti-Jewish hatred.
“We need to respond to this in the way Ian Austin and others have but also by way of a change in policy.”
A spokesperson for the Community Security Trust said: “This is vile racist intimidation against British Muslims, and we hope that those responsible are swiftly caught and properly held to account.”
The Jewish Council for Racial Equality said it was shocked to see the letters sent to Muslims.
Edie Friedman, Jcore director, said: "The presence of these letters reinforces, yet again, the need for different communities to come together and find practical ways of showing solidarity and support for one another.”