Chief executive David Potts said the retailer, which has branches across Swindon and Wiltshire, wanted the government to secure a tariff-free deal.
"Tariffs do drive inflation, so in any year no-one wants to see increased prices, particularly not as we are in a recession," he said.
The comments came as the supermarket chain reported that like-for-like sales, excluding fuel, increased by 8.7%, as it was particularly buoyed by rapid online growth.
Morrisons said it has expanded its online and home delivery capacity "five-fold" after the coronavirus crisis sparked demand for deliveries.
The group also launched new online propositions, including a partnership with Deliveroo which has now expanded to 180 sites.
Mr Potts said on Thursday that he believes we are seeing "the renaissance of British supermarkets".
He said: "From the start of the pandemic we stepped up and put the company's assets at the disposal of the country to help feed the nation.
"Morrisons is at the heart of local communities and responded quickly when it mattered most, and we are very grateful for the British public's appreciation of all the vital work our colleagues are doing.
"We are now looking forward to holding on to what we created in the first half, building on our colleagues' inspiration and innovation, and sustaining the momentum of a broader, stronger Morrisons."