Milk supplier Robert Wiseman has warned the cost of its new dairy in Somerset is likely to rise to £80m from £60m.
It blamed the increase on rising construction costs and its decision to increase capacity at the site from 300m to 500m litres a year.
The Scottish firm is pinning its hopes on the increased profitability it can achieve with the extra milk produced.
The news came as the company unveiled a 29.4% rise in pre-tax profits to £34.6m for the year to the end of March.
Wiseman said the Somerset dairy was on track to begin operations in December.