"We were deceived," the managing director of Findus France, Matthieu Lambeaux, said in a statement, adding that the company will file a suit against persons unknown on Monday.
Spanghero, the French supplier of meat for Findus lasagne, also said Saturday it was ready to sue the Romanian supplier.
Findus withdrew frozen meals in France and Sweden on Friday, a day after recalling frozen beef lasagne from British supermarkets.
And it admitted that French company Comigel, which produced lasagne and spaghetti bolognaise for Findus in Luxembourg after buying the meat from Spanghero, told it that the problem could date back to August 2012 in a letter dated 2 February 2012.
Earlier British Labour MP Tom Watson published on his website an extract from a letter that he claimed had been passed to him by a retailer.
"Investigations have led one of our suppliers based in France to inform us in writing on 2 February 2013 that the raw materials delivered since 1 August 2012 are likely to be non-conform and consequently the labelling on finished products is incorrect," it said.
Britain's Food Standards Agency announced Thursday that 11 of 18 samples of Findus beef lasagne were found to contain between 60 and 100 per cent horsemeat.
The scandal has since spread to Findus spaghetti Bolognaise.
British Food Minister Owen Paterson on Saturday said that he believed that there could have been an “international criminal conspiracy”.