The NDP is not interested in merging with the Liberals, the party's president and a potential leadership candidate said Wednesday.

"Our willingness to work with others to get things done in Parliament was a key part of our success in May. We shouldn't drop that," Brian Topp wrote in an email,"and we shouldn't adopt the Liberal 'we won't work with anyone – you have to vote for us' approach that served them so poorly."

Working with other parties does not mean merging with them, however, Topp said.

"That said, New Democrats aren't interested in becoming Liberals. The Liberals have been very clear that 'merger' isn't on their agenda. And it isn't on ours," he said.

Talk of an NDP-Liberal merger emerged this week as Liberals gathered on Parliament Hill for their summer caucus retreat and were asked about the idea. Most Liberals were shooting it down instantly, saying they are focused on rebuilding their party after being reduced to just 34 seats in the May 2 election and losing the title of Official Opposition. But Quebec MP Denis Coderre said Monday he thinks it would be a "valid discussion" for the two parties to talk about merging.

On Wednesday, he commented further and said those talks shouldn't necessarily be had now or in the near future. "I said eventually that's a debate to be made about what should be the future of the progressive forces, that's it. I didn't say that we will deal with it today," Coderre said on the last day of the Liberal caucus meetings.

"We will have to take a look at what will be the future of the progressive forces. And I said to explore all the options. That doesn't mean to merge. It means that it might be one of the answers," Coderre said. He noted that interim Liberal leader Bob Rae said a merger is not on the agenda and it wasn't talked about among the caucus. "End of story," he said.

On the NDP side, Manitoba MP Pat Martin made it clear that he wants the two parties to forge closer ties. He told Power & Politics host Evan Solomon on Tuesday that he wants to see the NDP and Liberals enter into a "formal co-operation" in the next election in order to guarantee a defeat of Prime Minister Stephen Harper and his Conservative government.

He said he wants someone in the upcoming leadership race to replace the late NDP leader Jack Layton to be pushing for that co-operation.

"That’s what I’m going to be looking for in the leadership race. I will support the candidate that advocates and even promotes a formal co-operation with the Liberals for the next federal election and if I don’t hear any candidate saying that, then I will throw my hat in the ring and I’ll be the unity candidate," Martin said.

Topp, the party president and longtime backroom NDP organizer, hasn't declared his candidacy, he's only indicated he's considering it.

But his comments Wednesday indicate that if he does enter the race, he won't be Martin's top pick.

One Liberal MP, in dismissing the idea of a merger Wednesday, said Martin was just trying to attract attention with his comments. "Pat Martin always likes to get himself out there, leading something, and I think he's taking the opportunity to get some press for himself," said Judy Sgro.

Rae said much of the discussion around Parliament Hill this week is "speculation on speculation on speculation."

"I don't want to get diverted into a discussion on what another party may be thinking about, or what another member of Parliament in another party might be talking about," he said.