Green Party Leader Elizabeth May says she's been trying for months to get the NDP to talk about ways the two parties can co-operate on shared priorities, but the party has kept the door firmly closed to her overtures.

She was reacting to NDP criticism over the announcement this week by May and Liberal Leader Stephane Dion that neither leader would run an opponent in the other's riding.

May is challenging Foreign Affairs Minister Peter MacKay in his Central Nova riding, hoping to win her party's first seat in parliament.

The NDP has called the move undemocratic, and former party leader Ed Broadbent revealed Friday that May had called former Canadian ambassador to the UN Stephen Lewis to try and get him to broker a deal with New Democrat Leader Jack Layton.

She admitted she has been frustrated with Layton's lack of co-operation, and turned to her old friend Lewis to try and open up the lines of communication.

"What the hell is wrong with Jack Layton that he can't answer a phone call?" she said on CTV's Question Period.

"I don't understand this. He talks to Stephen Harper all the time. Surely, our shared values are much closer between the NDP and the Greens."

She said the two parties should have been able to put partisan politics aside and focus on their shared environmental priorities -- such as solving climate change and reaching Kyoto greenhouse emissions reduction targets.

"We're not identical. We're different parties, but surely there's room for a conversation. And that's where I was disappointed," May said.

"Despite months of effort to open the door to any conversation at any level, not specifically Central Nova, not specifically what I could do for him or what he could do for me, but just to open the door -- and the door as far as I'm concerned is still open -- to discuss whether there was some way that despite our first-past-the-post system, leaders who care about their country and are willing to put the planet first can't find some way to communicate."

May also told Question Period co-host Jane Taber she was "sad" the NDP had dragged Lewis into the discussion. She said she would have never said publicly that Lewis was trying to help kick-start discussions.

May has maintained there were no backroom dealings with the Liberals, and said she was open and public about the fact that talks were taking place.

The NDP was incensed by those remarks, with Broadbent and others suggesting her calls to Lewis proved such backroom negotiations were underway. Conservatives and some Liberals were also angered by the news of May's deal with Dion.

May said she didn't consider her talks with Lewis to be backroom dealings.

She argued that she is just trying to do what Canadians have asked political leaders to do: put partisanship aside to work effectively on areas -- such as climate change -- that they all believe in.

The NDP announced Sunday that Louise Lorefice, a mother of eight and retired teacher from Antigonish, will be the party's candidate for Central Nova.

Lorefice hasn't previously run in the riding, though she has worked on NDP election campaigns for a number of years.

Former NDP Central Nova candidate Alexis MacDonald, who finished behind MacKay in the 2004 and 2006 elections, is concentrating on her work with the Stephen Lewis Foundation and is not running again, The Canadian Press reports.