Alliance leader Naomi Long has accused the DUP and Ulster Unionist leaders of desperation in holding secret talks to consider joining forces.
She said UUP leader Doug Beattie attempting to recruit the DUP's Sir Jeffrey Donaldson last year shows there is "not that much difference" between the two unionist parties.
And for Sir Jeffrey she claimed the discussions during leadership turmoil within his party further demonstrated that "self-preservation is his main concern".
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Mrs Long likened "gossipy" revelations of the encounter to "Eastenders only in Stormont", but she said it did not reveal anything new about the two leaders.
"Doug is desperate to grow the Ulster Unionist Party. Jeffrey is desperate to save his own skin in politics. Those are things we already know about both of them," she said.
In a Belfast Live interview ahead of the Alliance Party conference this weekend, she added: "It does though I think expose that there's not that much difference between the two parties despite all of the gloss and all of the claims that they're in very different places.
"If you're willing to discuss with somebody the potential of moving to work with them, I'm not so sure that there's a big gap between you in terms of your values and vision.
"I notice nobody's been courting me to go and join them because our values and our vision are distinct, they're strongly held and they know that they’re things that go to my very core."
Sir Jeffrey has insisted that while he was invited, he had no intention of rejoining the UUP last year after losing out in a DUP leadership battle to Edwin Poots.
But Mr Beattie said he initiated their meeting last June and it was organised to discuss the Lagan Valley MP potentially returning to the party he quit in 2003.
Soon after the meeting, Sir Jeffrey became DUP leader following an internal party revolt against Mr Poots.
Mrs Long said all party leaders want to expand their membership but she questioned whether Mr Beattie had considered how others in the UUP would react.
She said: "The question then is about whether or not he understands the kind of impact that would have on people who have long memories and remember when Jeffrey left the Ulster Unionists and the kind of damage that did at the time."
The East Belfast MLA also pointed to Sir Jeffrey's willingness to accept scrapped UK government plans to reintroduce double jobbing, allowing MPs elected as MLAs to keep their Westminster seats.
She said: "He wasn't willing to commit his career to the Assembly when things were uncertain. So we already know that self-preservation is his main concern."
Polls suggest Alliance could be set to make significant gains in May's Assembly election, with projections indicating it could become the third-largest party at Stormont.
But some have questioned whether its performance could be affected if the fortunes of the UUP are revived under the leadership of Mr Beattie, whose socially liberal values could appeal to Alliance voters.
Mrs Long said it was a "flawed analysis" to think that people would be voting UUP if they were not voting Alliance.
She questioned the "progressive" credentials of the UUP, citing how the party recently opposed an Alliance bid to fly the transgender flag at Armagh City, Banbridge and Craigavon Borough Council.
UUP councillors said they voted down the proposal from a "procedural point of view" due to the lack of a specific council policy on flying the flag to mark Transgender Day of Remembrance.
But Mrs Long said the "idea of being progressive isn't just something that the leader can talk about and then the rest of the party continues as usual".
The MLA said she was not suggesting the decision "reflects Doug's view, but it does reflect the Ulster Unionist view all too often".
"So what if you like has become a sort of media phenomenon around the leader isn't necessarily reflected in the delivery on the ground from the party," she said.
Last year East Belfast councillor Carole Howard quit Alliance to join the Ulster Unionists, saying she could now "openly and comfortably" express her pro-Union views.
Mrs Long said the councillor had "never raised any issue with us before" about feeling unable to express her opinions.
She said: "I had always been aware that she did have unionist views, so it didn't particularly surprise me that she felt comfortable in the Ulster Unionist Party, because I think it became clear that was her priority rather than the priorities of Alliance."
Mrs Long insisted party reps "always have been" able to openly express either pro-Union or Irish unity views.
And she said there was "no blockage on people being able to write articles" about the constitutional question, after former Alliance MLA Trevor Lunn last year claimed he had written a piece and the party "didn't want me to put it out".
Mrs Long said the party has engaged in various public debates and discussions about possible Irish unity as well as future constitutional arrangements within the UK.
She said that "it's not something that we shy away from, but it isn't what drives the party and it isn't what drives our politics".
"What drives our politics is creating a united Northern Ireland because I don't know how you can have a United Kingdom in any meaningful way, or a united Ireland in any meaningful way, if the people of Northern Ireland are still bitterly divided."
Mrs Long said after the election her party ideally "want to be in government", although she did not completely rule out going into opposition.
The Justice Minister warned against a lengthy delay in re-forming a power-sharing Executive after the poll in May.
"I think the worst possible outcome for the people of Northern Ireland is a very long hiatus after the election with no government in place," she said.
"I don't think that's sustainable and I think it's a real lost opportunity if we end up in that space."
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