Hundreds of pig farmers from across the country will be flying the flag for high-welfare British pork today outside the Houses of Parliament.

After the mass rally in Whitehall, which is being supported by producers from East Anglia, Yorkshire and the West Country, a 'Pigs Are Still Worth It!' petition will be presented to Number 10.

With producers losing �21 on every finished pig because the price of wheat has doubled to about �200 per tonne, the industry is set for further collapse in its traditional East Anglian heartland, warned a leading auctioneer and consultant.

Peter Crichton, who is also an industry commentator based at Bury St Edmunds, now has instructions to sell five large-scale units in the coming weeks. 'At the same time last year, I had just one producer selling up,' he added.

The surge in the feed wheat price in the past nine months, which accounts for about 70pc of costs of finishing a pig, has sapped returns. Today, a new-born pig will cost a producer at least �21, according to industry body the British Pig Executive.

And there is no hint of any light at the end of the tunnel as the gap between feed costs and returns has widened, said Mr Crichton.

'It is looking serious because it is the biggest sustained gap between the feed price and the pig price. And if we want to have any form of sustainable home-production of pork, then something has got to happen now,' he added.

He is not optimistic given that the industry measure of finished pig prices has fallen steadily since last June from 146.7p per kg to 135p per kg this week. And animal feed prices, driven by wheat in the same period, have soared from roughly �100 to �200 per tonne.

As farmers have come under greater pressure, a roadside poster campaign was launched. More than 270 signs have been placed alongside major trunk roads to bang the drum for the pig sector with slogans including 'Yes! Yes! Yes! to British Pork' and 'Made in Britain – perfect British bacon.'

One example can be seen off the A47 on the southern bypass alongside Andrew Haag's outdoor pig unit of some 750 sows at Caistor St Edmund while father and son, Jimmy and Alastair Butler have placed banners on trailers by the A12 at Blythburgh, near Halesworth.

It is a measure of the industry's determination to emphasise the welfare advantages of home-grown production to consumers, and indirectly to retailers.

Since the ban on sow stalls and tethers was introduced more than 10 years ago, half the UK's pig industry has been lost – and production effectively exported abroad with a consequent impact on the balance of payments and, of course, jobs too.

'We're now importing more and more and it doesn't make sense,' said Chris Fogden, a leading East Anglian producer, who is a key board member of the National Pig Association. He runs 1,000 outdoor sows on the Duke of Grafton's Euston estate, near Thetford, and will be joining the London rally.

Mr Fogden, who has been in the industry for more than 20 years, is faced 'a dramatically reduced price when his current contract ends in a few weeks' time.'

He specialises in producing weaners, or young pigs, which are reared to about 30kg, for finishing. He argues that the industry's fortunes could be transformed by a fairer distribution of returns back down the chain to the producer. 'We're not just asking for more at the retail end.'

It's a point also made by Mr Crichton. 'We can't expect government to tell the supermarkets to pay pig farmers more. They're all fighting price wars with each other.

'My own view is that the government can play a part by implementing fairer labelling, and it has gone some way down the track. But government could also put more pressure on departments and local authorities to buy more home-grown pork for schools and the armed forces,' he added.

But it does not solve the more immediate problem for the pig farmer, who is buying rations at today's prices.

'An old rule of thumb, which isn't too far out, states that the price of pigs needs to match the price of wheat,' said Mr Crichton.

'If the wheat price is �167 per tonne, we need a finished pig price of about the same level. Currently the DAPP (Deadweight Average Pig Price) is about 136p per kg – that's the measure of the gap.'

Two other factors have not helped. First, stocks of pigmeat in Europe are still running at high levels, and second, Europe has just scrapped a scheme to take pig carcases off the market.

But the battle to win consumer support will continue. And more roadside banners promoting farming's Red Tractor symbol, which shows food has been produced on British farms to high welfare, environmental and safety standards, are set to appear.