Amazon spent more than $3 million on anti-union consultants last year in its continuing effort to keep organized labor out of its delivery network, according to disclosures filed Saturday with the Labor Department.

The Seattle-based retail giant has been ringing up a large tab hiring “persuaders” who try to convince workers not to form unions. It doled out more than $14 million on such consultants last year as well.

Employers are required to disclose such spending when the consultants speak directly to workers about unionization. The figures cited in the forms generally would not include money Amazon spent on in-house work against unions or legal advice aimed at undermining organizing efforts.