Police in New York are investigating an alleged hate crime after an African American family received an anonymous note asking them to leave the town where they live.

The Copes were asked to leave Lindenhurst on Long Island, which the letter claims is “84 per cent white”.

“Attn: African-American family,” the note written in capital letters says. “This is coming from Lindenhurst community.

“You don’t belong here. Please leave Lindenhurst as soon as you can. It will be better for all of us. Find the town where there are more people like you.”

Darcell Copes lives with her children and grandchildren (Darcell Cope/Facebook)

The message ends with a bizarre apology: “Sorry if this is rude, but it’s the truth.”

Darcell Copes, who lives with her three adult children and five grandchildren, called the writer of the letter a “coward” but said she would pray for the person.

"I went from being fearful, protecting my family, to being totally confused, and wanted to know who and why," she told NBC 4 New York on Friday.

The Copes family have lived in Lindenhurst for the past two years (Ronica Copes/Facebook)

"Today, it becomes even deeper: is it someone in the school district, is it the guy at the corner store, is it my neighbour down the street? Where?"

Ronica Copes, Ms Copes’ daughter posted the letter on Facebook, where it has been shared more than 1,400 times.

Ronica Copes posted the letter her family received to Facebook (Ronica Copes)

She wrote: “Sooooo, I'm checking my mail and when I come across this I can't help but laugh...wait, it's not funny though. Where they do that at? Oh yeah Lindenhurst. Unbelievable but then it's not...our daily reality, I've just never seen it in this form.”

The Copes, who have lived in Lindenhurst for two years, said the community had been supportive after the letter, but it demonstrates the racism still experienced by many in small-town America.