As many as 300,000 British hens are still being housed in battery conditions, despite a European-wide ban coming into force earlier this month.
Figures from Brussels showed that some 30 farms in Britain are still using battery systems.
Defra said last night that any farms found to be still using cages for hens could face a fine of up to £2,500 and six months imprisonment.
The figures, while only equivalent to around one per cent of the country’s entire hen flock, are a blow to the British farming industry which has worked hard to phase out battery systems, with British farmers having spent £400m in the process.
As many as 14 other EU member states have failed to phase out cages for hens, provoking anger from UK farming leaders worried that domestic producers would be undercut in price by cheap battery farmed eggs from abroad.
Farming Minister Jim Paice has resisted calls for an import ban, however, instead encouraging retailers to voluntarily agree to not stock products made from battery-farmed eggs.
A Defra spokeswoman said: “By February 1 we expect that these producers will have stopped using these battery cages or we will have issued legal notices and referred the producers to the local council who will consider prosecution.
“It is disappointing that a small minority of egg producers have not yet made the necessary changes when the rest of the industry has spent £400m to improve welfare and meet these standards.”