Ms Lucas, who previously led the party and is its first MP, said her personal view was that candidates that endorsed a core of shared policies should work together across party lines.
“One strategy … might be to consider the potential for progressive pacts,” she wrote in the Guardian newspaper.
“A possible first step could be for Labour, Greens, Lib Dems, the SNP and Plaid Cymru to empower local branches with the ability to back candidates from other parties if they wish.”
The multi-party pacts would see candidates from across the Left endorse one another, with different parties standing down in different seats.
Ms Lucas said that such cross-party candidates could in a “transparent and open way” sign up to a series of core policy pledges as a condition of support from other parties.
The plan would help left-wing candidates win seats under Britain's antiquated first past the post electoral system.
Conditions of Green Party support would action on climate change, recognising society’s ecological limits, and taking a firm stance against austerity, she suggested.
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Ms Lucas also added that a commitment to support electoral reform at Westminster would be required from any candidate.
She warned that many Labour or Liberal Democrat candidates were unlikely to be approved by local members, however. Local parties would have the final say.
The proposal would not be the first time local Green Party branches have endorsed other left-wing candidates.
At the 2010 election the party’s Birmingham Hall Green branch stood down to support Respect candidate Salma Yaqoob.
At the 2015 election Ms Lucas increased her majority in her Brighton Pavilion constituency, winning 41.8 per cent of the vote, up on 31.3 at the last election.
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