The French president François Hollande has called for compulsory labelling and traceability of meat used in processed foods in Europe to prevent a repeat of the horsemeat scandal.

Speaking at the start of the Paris agricultural fair on Saturday, he said: "There needs to be traceability – that is what I want from talks on a European level. We need compulsory labelling on meats that will be used in processed foods."

Agriculture ministers from France and Germany agreed on Friday the need for origin labelling and said they would try to find a deal on meat traceability at a meeting of European farm ministers in Brussels on Monday.

Hollande said that while waiting for European legislation, France would encourage voluntary initiatives to improve labelling.

The president's comments come after more traces of horsemeat were found in British food supplies. Horse was found in burgers in a North Lanarkshire school kitchen while burgers in Welsh schools were supplied by a factory which was implicated in the horsemeat scandal.

Sodexo, one of Britain's largest private catering suppliers which provides food for public services including the armed forces, schools, care homes and prisons, has withdrawn all frozen beef products across most of its business after the discovery of horse DNA in one of the samples it tested.

On Friday Birds Eye withdrew a range of beef products as a precaution after its chilli con carne was found to be contaminated by horse DNA.

The scandal, which has triggered recalls of ready meals and damaged confidence in Europe's vast food industry, erupted last month when tests carried out in Ireland revealed that some beef products contained horsemeat.

The French industry body for horse butchers, Interbev Equins, estimates there has been a rise of up to 15% in horsemeat sales since the scandal broke. With French customers now wary of ready meals – frozen food sales are down by 5% in France, and trade at organic stores has risen – shoppers have been flocking to traditional artisan butchers, particularly to get horse.

About 16% of French households buy horsemeat, consuming about 20,000 tons a year.