CO-OPERATION between the Green Party and Plaid Cymru was on the brink of breakdown yesterday after nationalists were accused of “social media harassment.”

The parties have formed a so-called “anti-austerity alliance” with the SNP and hope to hold the balance of power in Parliament after the general election.

Plaid’s campaign chief Dafydd Wigley has even appealed for Welsh ex-pats in England to vote Green in May.

But the deal is in danger after Welsh Green leader Pippa Bartolotti claimed at the weekend that she has been the victim of “online bullying” from Plaid members.

She said she had been bombarded with messaged from Plaid members angry that her party won’t stand aside in Ceredigion.

The parties stood a joint candidate in the constituency in 1992 and the Star revealed in October how Plaid are keen to revive the electoral pact.

Ms Bartolloti said in her statement that she met Plaid leader Leanne Wood for talks but refused to stand aside for Plaid’s Ceredigion candidate Mike Parker.

And she said: “The harassment and online bulling from certain Plaid Cymru members has increased. We are all fed up with it.

“Clearly Plaid Cymru are terrified of losing Ceredigion. This is not our problem.”

Hitting back yesterday, a Plaid Cymru spokesman said: “We don’t recognise the comments made.

“From what we have seen on social media and on the streets throughout the country, it seems many people concerned with the environmental and traditional green politics will be backing Plaid in May.”

Labour AM Mick Antinow seized on the spat, saying the parties were “at war.”