Horwath has repeatedly blasted the Liberals for cancelling two gas plants in the days before the 2011 election, a move that could eventually cost the province up to $1.1 billion.
She says Premier Kathleen Wynne, who was a senior cabinet member at the time, signed off on the decision, but stopped short of calling the premier corrupt.
Wynne is suing Progressive Conservative Leader Tim Hudak over comments he made in March suggesting she "possibly ordered'' the alleged destruction of government documents related to the gas plants scandal.
But Horwath today brushed off concerns that she could face a lawsuit, saying she is more worried about ensuring Ontarians have "a government they can actually trust."
Wynne called the allegations "sad" on Monday but said she wasn't planning to sue the NDP leader.