A Reclaim Australia supporter has been charged with threatening to slit the throat of a prominent Sydney lawyer and campaigner against Islamophobia.

Mariam Veiszadeh​ reported the online threat to NSW Police, who last week charged a mother-of-three from Guildford with using a carriage service to menace, harass or offend.

Reclaim Australia demonstrators in Martin Place in July. Credit:Michele Mossop

In a private message sent to Ms Veiszadeh on Facebook, the 37-year-old woman allegedly said she would "find you and hunt you down".

"Watch as we come for you in your sleep [and] cut your throat as you do [to] the animals you torment," said the rambling message sent at 11.06pm on July 12.