Frederick Owusu, Principal
Tel. 01733 977520
It follows reports the firm has lobbied the regulator to allow it to raise bills by 40% and face lower fines.
The former sub-postmaster told the BBC that the Post Office's business model is "dead in the water".
Nearly two-thirds of callers to the tax authority had to wait longer than 10 minutes to get through.
It is predicted the huge factory will create 4,000 jobs and many more in the supply chain.
The firm never acknowledged the project publicly but had recruited about two thousands workers.