Federated Farmers is investigating whether its members were involved in making threats against a newspaper columnist.

Rachel Stewart has received malicious letters and threats of rape, after a column criticising farmers was published in the Taranaki Daily News last week.

William Rolleston says Federated Farmers is making its own enquiries.

The organisation's president says they haven't been able to verify whether certain comments have been made by members, or if members were involved in encouraging the discussions on Twitter.

Mr Rolleston says he takes the matter seriously, which is why they're looking into it independently.