Unions Brexit campaign decision 'mistake', claims Wood
The first minister refused "to use his greatest campaigning tool" during the 2016 EU referendum campaign, according to the leader of Plaid Cymru.
Leanne Wood said Carwyn Jones rejected calls to use the trade unions because they were "too busy" working on Welsh Labour's assembly election campaign.
Mr Jones said he thought it was "naive to have a cross-party campaign in the middle of an election."
The exchanges came in a debate marking two years since the EU vote in 2016.
Welsh political leaders were united in their objections to holding the EU referendum just seven weeks after the Assembly election.
But the first minister told AMs on Tuesday: "We spent all our time knocking lumps out of each other as part of a democratic process - the electorate aren't going to buy a week later that we're suddenly all friends again.
"She and I, on this issue, are on the same side. She reminds me of somebody playing in a rugby team who runs around the pitch trying to tackle members of her own side rather than focussing on the opposition."
He was responding to accusations from the Plaid leader that "Labour is pursuing a Brexit that aligns more with the Conservatives than the white paper co-authored with Plaid Cymru".
In the debate, Ms Wood said it was also a time to reflect on the campaign as she recalled approaching the first minister with a proposal "to put in place the infrastructure for a Welsh Remain campaign made up of representatives of Welsh civic society".
"I proposed that the trade unions should form the core of this group with their vast reach and interest in a 'remain' vote," she said.
"My offer to the first minister was a genuine one: 'Join with me to build a civic society organisation to campaign for a 'remain' vote'.
"It was always going to be difficult to advocate for the status quo. We needed to organise, organise, organise.
"I was told by the first minister that the trade unions are too busy campaigning and fundraising for Labour for the Assembly election. The first minister refused to use his greatest campaigning tool, the unions and others, for the national good.
"The first minister was confident that Leave would not win: 'Look at all the other referendums,' he said. Well, look where we ended up."
She said Labour had failed to use the office of first minister to pull together a successful campaign, as had happened in the 2011 and 1997 assembly referendum campaigns.
"Had you done that we might have had a different result and I wonder if you regret that now," added Ms Wood.
Labour's AM for Llanelli said he was "surprised it's taken her two years to reveal this cunning plan".
Lee Waters added: "It misunderstands the depth of feeling amongst our own constituents about what that referendum was about, that if only a couple of well-meaning worthies came together and got a little campaign going, all would've been well.
"I think it's dangerous thinking to dig this up to try and score political points to suggest that she had the answer all along," he added.