As the price of hot roast chicken soared by 20% this week, Morrisons pledged to continue its campaign calling on ministers to reverse the controversial VAT ruling.

Under new tax rules that came into effect on 1 October, rotisserie chicken now costs an extra 80p - a hike that the retailer said would force six in every seven families to either cut back or stop buying them altogether.

Morrisons, which launched a ‘Don’t Tax our Roast’ campaign with the British Poultry Council last month, plans to present a petition signed by more than 40,000 people opposing the move to ministers in the next month. “We had more than 40,000 signatures at the last count but we’re still going through them,” a Morrisons spokesman said.

In-store trials by Morrisons revealed a 9% decrease in volume sales when the 20% rise was applied - a move expected to cost the industry almost £20m.

Siobhan Freegard, founder of parenting website NetMums, said the tax hike would simply force some families to switch to cheaper and unhealthier alternative foods.