York for Europe had claimed that Liberal Democrat supporters had promised to vote Labour in York Outer, where the Tories had a majority of 8,289 under Julian Sturdy.
And it was claimed that Labour supporters had pledged to vote for the Liberal Democrats in Harrogate and Knaresborough, where sitting Conservative Andrew Jones won in 2017 with a majority of 18,186.
It was alleged that Labour and Liberal Democrat supporters met in York and Harrogate on Wednesday to finalise their pledge in the vote-swapping alliance when posters were displayed.
North Yorkshire for Europe said in a tweet: "We decided against using real ones (posters) so we cant be accused of misrepresenting Lab (or Lib Dems in York) by using their official merchandise. This action not sanctioned by the Labour Party, the Lib Dems or anyone else. We're just cross party ordinary people."
Mark Sewards, Labour candidate for Harrogate & Knaresborough, said: "Labour are the only party offering a real alternative to the Conservatives in Harrogate and Knaresborough and we are the only party offering a public vote on the final Brexit deal.”
A spokeswoman for Harrogate & Knaresborough Constituency Labour Party, said: "The local Labour Party were not consulted at all regarding this latest 'display' organised by the Lib Dems and North Yorkshire for Europe yesterday (Weds Dec 11) lunchtime in Harrogate town centre, which saw official Lib Dem posters used and fake hand-made, hand-written Labour ones held aloft - in some cases by members of other parties who actually told us yesterday that they had never voted Labour in their lives.
"Indeed, once we were made aware of the 'display', we set up our own, supporting our own excellent Labour candidate, Mark Sewards, and opposing tactical voting generally in this non-marginal constituency, and where Labour were neck and neck with the Lib Dems at the last general election.
"It is important that members of the public are made aware of this charade as we were inundated with messages from confused voters (on Wednesday) evening."
Andrew Hollyer, campaign organiser for York Liberal Democrats, said: "It is nothing to do with us and we don't support it. Lib Dems in York Outer will be voting Lib Dem.
"It is very disappointing. We have had quite a good working relationship with York for Europe for a few years."
Martin Brooks of York for Europe and Richard Sadler of Yorkshire for Europe, said in a joint statement: "The supposed row about event this is both overblown and misguided.
"Both York and North Yorkshire for Europe groups are non-party political, pro-Europe groups.
"What our members have in common is they wish to see Brexit stopped. This depends on the Tory party not gaining a majority in this General election .
"The whole point of our event was to advocate a collaborative way of working between two opposition parties’ that the party leadership themselves have not successfully achieved.
"Instead they have torn strips of each other putting party interests before the country's. We make no apology for encouraging people who want to put country before party to exercise a democratic choice and suggesting a way to do this.
"Voters have been thoroughly exposed to the idea of tactical voting before and since the calling of the General Election.
"It is a democratic choice for voters, of any historical voting allegiance, for whom remaining in the EU is their primary objective.
"Up to now 'the tactical vote' has been thought of in response to historical voting patterns inside each constituency ie, which contending party vote was in recent elections closest to the majority vote holder.
"The fact we have provoked a hostile response in equal measure from both political parties is evidence that they find it impossible to put aside tribal instincts even when the future direction of the county is at stake.
"What we did was offer a different way of looking at tactical voting that took a cross party, cross constituency view of the political landscape to achieve an outcome of potential benefit to both parties. It is a regret the parties do not look past their local rivalries to a bigger prize.
"Our invitation to people to consider tactical voting using a visual representation of what we were suggesting does not require nor did we claim it had, the endorsement of any political party."