Internal dissent over the Ontario NDP's poor election result has spread to the party's caucus, with two MPPs saying the party must return to its left-wing roots as it struggles to hold on to its traditional base.

Battling to contain the fallout, Leader Andrea Horwath on Tuesday called the loss of three Toronto seats "very, very troubling" and vowed to make changes.

"We have some lessons to learn from that campaign. We have some work to do to engage some activists, particularly in the Toronto area, to spend some time reflecting on the feedback that they're giving us and to use that feedback to make some changes," she said. "The result of this election was bittersweet. We lost seats in Toronto – very, very concerning for us –all three of those MPPs were very good MPPs and they lost their seats. That's very, very troubling."

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Some grassroots organizers have long been unhappy with the populist direction Ms. Horwath has taken the party. That anger has escalated since the election, which Ms. Horwath forced in May by rejecting the then-minority Liberals' budget. The Grits subsequently won a majority and the NDP consequently lost the balance of power in the legislature.

Ms. Horwath's critics are angry that she has emphasized small-ball policies – such as hydro bill rebates – over big-picture ideas.

The Liberals, meanwhile, campaigned from the left, emphasizing a new pension plan, public transit and a higher minimum wage. They took a bite out of the NDP vote, unseating MPPs Michael Prue, Rosario Marchese and Jonah Schein.

"We had a very difficult time in Toronto and I don't think that our message was one that was crafted for Toronto," MPP Peter Tabuns, one of the NDP's two remaining Toronto MPPs, said at Queen's Park Tuesday. "People were very concerned that they didn't hear a Toronto voice. They didn't hear a strong message on transit."

Mr. Tabuns said the party "should be speaking about social justice" more than it did during the campaign.

MPP Cheri DiNovo, who held her inner city Toronto riding in the face of a tough Liberal challenge, said the NDP has compromised its values in a bid to appeal to conservative voters outside Toronto.

"It was a debacle from the beginning, from day one," she said in an interview with Torontoist, the online newsmagazine. "Many of our supporters – who voted Liberal – saw more progress in the Liberal budget than they saw in our platform. That was a core mistake."

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Disgruntled grassroots members have already been meeting. At one get-together late last month, at the Steelworkers Hall in downtown Toronto, party rank and file discussed replacing party executives and other top officials, but decided it would be too divisive to challenge Ms. Horwath's leadership, said a source who was in the room.

Ms. Horwath's office is also going through a shakeup. As The Globe first reported Saturday, the prime architect of the election campaign and another top aide are both on their way out the door. Long-time chief of staff and campaign manager Gissel Yanez, and principal adviser Elliott Anderson, are both scheduled to leave over the summer.

But Ms. Horwath has so far been reluctant to show much public contrition over the results. That changed Tuesday, as she acknowledged the Toronto losses were "concerning."

"What we need to do is grow from this experience and that's why we're engaging in the discussion with our activists both in Toronto and around the province," she said. "We do take seriously the loss of the seats in Toronto and we're going to work very, very hard to engage with Toronto activists and others to make sure that we're learning."

The party has already been tacking left since the election. This week, she repeatedly criticized Liberal proposals to cut spending as too extreme, even though her campaign platform actually envisioned slashing spending by $600-million per year more.