Mr Lenox, a software engineer from Keswick, says he is opposed to nuclear power and has pledged to campaign for a “safe energy future” and for Britain to maintain a close relationship with Europe.
Jonathan Bartley, party co-leader, said: “Jack is giving people in Copeland the chance to vote for a candidate who opposes nuclear power, believes in Britain having a close relationship with Europe and fights for a truly public NHS.
“No other party is able to offer voters this clarity on the big issues facing the area.”
Mr Lenox added: “I’m delighted to be selected to contest this by-election.
“Copeland has borne the brunt of Government funding cuts and healthcare is currently facing stark challenges.
“We will also suffer if Theresa May yanks Britain out of the single market and turns our country into a corporate tax haven.
“The Green Party is the only party with truly progressive solutions to the issues Copeland faces.
“It’s a privilege and an honour to represent the Greens as a beacon of hope during this turbulent period in British politics.”
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