There are an estimated 70,000 horses unaccounted for in Northern Ireland, the British Labour Party has claimed as the Government there sought to allay fears that contaminated meat was being sold in supermarkets.

Shadow environment secretary Mary Creagh said unwanted horses were given false paperwork in Northern Ireland before being sold for €10 and then resold to dealers for meat for as much as €500.

She said there was currently a "lucrative" trade in horses, claiming that while the Polish and Romanians were being "conveniently" blamed for the scandal, the contamination problem had started across the Irish Sea.

Speaking in the Commons, Ms Creagh said: "The Ulster Society for the Prevention of Cruelty to Animals have clear evidence of an illegal trade of unfit horses from Ireland to the UK for meat, with horses being re-passported to meet demands for horse meat in mainland Europe.

"It says that there are currently 70,000 horses unaccounted for in Northern Ireland. Unwanted horses are being sold for €10 and being sold on for meat for €500 - a lucrative trade.

"It is very convenient to blame the Poles and the Romanians but so far neither country have found any problems with their beef abattoirs."

Many horses are also believed to be contaminated with the carcinogen phenylbutazone, often referred to as bute, she said, claiming that the Environment Secretary Owen Paterson had been "incompetent".

The lack of information from the Government had been a "disgrace", Ms Creagh added, telling MPs the British public's confidence in the food chain was "sinking like a stone".

Mr Paterson said that unless products had been designated as unsafe by the Food Standards Agency, consumers should not worry.

Turning to Ms Creagh, he said: "The advice on food is very, very simple. I have been completely consistent on this. I have been absolutely clear, the independent agency which gives professional advice is the Food Standards Agency.

"I, you, MPs, and the public should follow their advice - so as long as products are free for sale and they have not been recommended for withdrawal by the Food Standards Agency, they are safe for human consumption."

Moments earlier, Mr Paterson told MPs it appeared that "criminal activity" had been at the heart of the scandal.

He said there would be immediate testing of products across the supply chain, telling the Commons this would also include tests at schools, hospitals and prisons.

The FSA had also reassured him that the products recalled did not present a risk to the public, but consumers who had bought Findus beef lasagnes should return them to the shop they had bought them from as a "precaution".

He said the "ultimate source" of the problem was not yet known but agencies were investigating a supply network that stretched across Europe.

Mr Paterson said: "At the moment this appears to be an issue of fraud and mis-labelling, but if anything suggests the need for changes to surveillance and enforcement in the UK we will not hesitate to make those changes.

"Once we have established the full facts of the current incidents and identified where enforcement action can be taken, we will want to look at the lessons that can be learned from this episode.

"I want to re-iterate that I completely understand why people are so concerned about this issue. It is unacceptable that people have been deceived in this way. There appears to have been criminal activity in an attempt to defraud the consumer.

"The prime responsibility for dealing with this lies with retailers and food producers who need to demonstrate that they have taken all necessary actions to ensure the integrity of the food chain in this country."

Ms Creagh accused the Environment Secretary of not taking the situation seriously enough as he had to be called back to London from a long weekend last Friday to deal with the crisis.

She also claimed the Environment Agency and police failed to act on information she provided that three British companies were involved in potentially importing beef that contained horse.

The information was handed to the Serious and Organised Crime Agency but there was no "live" investigation.

Mr Paterson also failed to share the names of the three companies with industry leaders during a meeting on Saturday, Ms Creagh told MPs, adding the Government was "dangerously complacent" about the situation.

It was not good enough for there to be a 10-week delay before the results of the first tests are known, she added, as she accused Mr Paterson of "hiding behind civil servants".

Ms Creagh added: "The French government estimates that the Findus fraud alone has netted criminals €300,000. This is clearly big criminal business."

Meanwhile, there was evidence that contaminated meat was entering the food chain from the UK and via Ireland rather than the rest of Europe.

PA Media