TORONTO _ Ontario's Superior Court of Justice has given the green light to a $10-billion class action lawsuit targeting the federal government for economic losses caused by a 2003 outbreak of mad-cow disease.<

Justice Joan Lax certified the suit by 115,000 cattle farmers on Thursday.<

She said the evidence they have amassed ``speaks to the enormity of the economic consequences to cattle farmers'' from the outbreak, which effectively prevented Canada from exporting any meat products for several months.<

The suit accuses federal inspectors of negligence, saying a government program designed to monitor imported cattle failed to prevent potentially infected cows from entering Canada and becoming part of the cattle food chain.<

Mad cow disease is transmitted when healthy cattle eat food containing the remains of infected cows.<

The case will proceed to trial unless the defendants choose to settle.<

In her ruling, the judge explicitly rejected a federal argument that a messy courtroom battle could play into the hands of the U.S. cattle lobby, which hopes to permanently close the border to Canadian beef and cattle products.<

``This may be a difficult political decision, but it is not a reason to deny certification,'' Lax said