The pig sector has responded with concern following a reduction in the proportion of British products on display across the big retailers.
The proportion of British pork products displayed by UK retailers fell in November, although it remains ahead of 2021 levels.
The latest AHDB Porkwatch survey shows fresh pork facings across the 11 retailers surveyed at 85% British, down from the recent high of 87% in September.
The National Pig Association (NPA) said it was 'disappointing' to see a reduction, with the figures showing that support was 'starting to slip'.
The figure for bacon was down from 63% in September to 60% but compared favourably with the 54% of November 2021.
And the proportion of British ham fell more significantly from 73% in September to 65% in November, slightly up on a year ago.
Sausage was the only category to record an increase on September, up slightly to 88%, remaining above year earlier levels.
In terms of fresh pork, Aldi, Co-op, Lidl, M&S, Morrisons and Sainsbury’s all recorded 100% British, with Waitrose on 99%.
However, Asda recorded a substantial reduction in British fresh pork, down from 66% in September to 58%, with Tesco dropping from 75% to 73%.
M&S recorded 100% across all categories, with the Co-op at 100% across three categories and 92% on sausage and Waitrose between 93 to 99% for the four categories.
Notable support elsewhere came from Aldi, which the survey showed stocked 100% British sausage, with Lidl at 86%.
NPA chief executive, Lizzie Wilson said all retailers must improve their sourcing and pricing policies to "give hope" to UK pork producers.
She warned that farmers had "taken a battering" over the past two years, and retailers must help stop a further contraction of the UK pig herd.
“We have seen better support for British pork products in recent months, certainly compared with last year, but the November survey suggests this is starting to slip.
"As always, we thank those retailers who continue to back our beleaguered British pork producers, in some cases with 100% British or close to it across the categories.
“But as we approach the traditionally difficult New Year period for the pork market, we urge all retailers to take a long-term perspective in their sourcing and pricing policies."
It follows new Defra figures which show that the UK pig breeding herd has sharpy declined as producers in the sector continue to be severely challenged.
The total pig population fell 2.5% in 12 months, to 5.19 million head, according to the figures detailing the UK's livestock population.
Overall breeding herd contracted 15.2%, driven by a loss of 56,000 sows (-14%) in the female breeding herd which stands at 342,800 head.
