At last month’s Caerphilly by-election, which was won by Plaid Cymru, the Greens came fifth with just 1.5% of the vote.
Slaughter has put his party’s weak performance down to tactical voting aimed at stopping Reform in a first-past-the-post vote.
“I don’t think it’s a reflection of our support in the area…a lot of people voted with their brain, perhaps not their heart,” he said.
Slaughter added he was “relieved” that Reform had not won the by-election.
Recent polling suggests Plaid Cymru and Reform are competing to be the largest party at the election in May.
However, given the new voting system makes it highly unlikely any party will win a majority, any Green MSs could have “a disproportionate amount of influence and power”, Slaughter said, and he suggested his party would be prepared to work with Plaid.
“Plaid would be the obvious choice.
“Obviously we’re never going to work with Reform or the Conservatives.
“I don’t think there’ll be much of a Labour Party there to even think about working with,” he added.
“But, as I’ve said before, there are all sorts of ways of parties working together.”
Following the 2021 Scottish Parliament election, the Scottish Greens entered into a coalition with the SNP, but it collapsed in 2024 after the Scottish government scrapped climate change targets.
