Commons food investigators discovered that the chickens, sold as organic - and at a premium price - had come from an ordinary farm.
The organic menu featured chargrilled breast of chicken served with red peppers, spinach and red kidney beans at pounds 8.50. The truth about the chickens was not discovered until dozens of MPs and their guests, some of whom were farming experts, had eaten the food.
The MPs' food supplier, who has worked for the Palace of Westminster for years, is said to be "mortified" and "scandalised".
Some MPs feel swindled. "This disgracefully devalues organic farming," said Norman Baker, the Liberal Democrat food spokesman. "People are increasingly turning to organic food as a rejection of chemical farming. We need to have absolute confidence in organic labels. The Leader of the House [Margaret Beckett] should prosecute herself under the Trades Descriptions Act."
The Commons caterers have turned to the Soil Association, which gives a seal of approval to organic farms, for help. "Basically they wanted to find out what was meant by organic chicken and poultry and to make sure that their organic menus were the genuine article," said Harry Hadaway, the association's spokesman. "We sent them a list of certified poultry producers. I understand there was confusion about what does constitute organic poultry."
Organically reared chickens are not fed antibiotics, growth hormones or artificial food. They have access to outside space and their corn is not sprayed with fertilisers or pesticides. The land are reared on must have no residual pesticides, which can take two years to disappear.
"The chicken we bought as organic turned out not to be," said Sue Harrison, the Commons' director of catering. "We are very concerned and our own supplier was absolutely scandalised. We have been using him for years. There is racket potential here, because farmers can charge a huge premium for organic produce and it is difficult to discover the truth because of the long distribution chain. It is very difficult for caterers to find genuine organic supplies. We are very thorough about our food, and luckily we checked."
The menu was only for MPs and their guests - not researchers or civil servants. Its introduction followed speeches in the House calling for more Government backing for organic farmers, requests from MPs for traditionally produced food, and more varied menus.
The dining rooms now feature British regional dishes. Last week's special was jellied eels.
"It's not the greatest state of affairs, but you have to give them full marks for trying to get organic produce," said Angela Smith, Labour MP for Basildon. This week "organic fish" is on offer.Reuse content