The pair say they want to form a 'progressive alliance' with Labour, to stop the Conservatives being re-elected.
Results of a ballot of members, announced at the party conference in Birmingham on Friday showed they took 88 per cent of the votes cast.
Addressing the future of the party and the benefits of having co-leaders, Mr Bartley said the Greens would be "more united with two leaders than other parties are with one".
In a swipe at the Conservatives and Labour, he said: "If we do disagree, we talk about it and resolve the problem.
"We don't throw the country's security and stability away to settle an internal squabble.
"And we don't throw bricks through one another's windows.
"We are united in our passion for doing politics with people."
Jonathan Bartley founded Ekklesia in 2002 as an organisation which "orients its work around the changing role of beliefs, values and faith/non-faith in public life".
In that role, he was regularly used as a commentator in the mainstream media on issues relating to the Church.
He joined the Green Party in 2011 but was previously part of John Major's campaign team in the 1995 Conservative Party leadership election.