Green Party MP Caroline Lucas is to stand for the leadership of her party as part of a job share.

Ms Lucas, who previously led her party between 2008 and 2012, will run for the post jointly with Jonathan Bartley, the party’s welfare spokesperson.

The pair hope to succeed Natalie Bennett, who said she would not be re-standing for leader at the end of her current term this summer.

The MP and her running-mate say they want to build a one-off “progressive alliance” at the next election to defeat the Conservatives.

Such a plan could potentially see the Green Party and Labour standing down in each others’ marginal seats or choosing a unity candidate in order to beat the Conservatives.

A suggested condition of such a pact has been electoral reform and the introduction of proportional representation.

Ms Lucas said job sharing for the role would allow her to focus on her constituents in Brighton while leading the party.

“Jonathan and I are seeking nominations as co-leaders because we believe that by sharing power and working together we'll be more effective than either of us would alone,” she said.

Policies: Where the Greens stand on the major issues Show all 13 1 /13 Policies: Where the Greens stand on the major issues Policies: Where the Greens stand on the major issues Taxes Wealth tax of up to 2 per cent on the assets of 300,000 people who are worth more than £3m, the country’s richest 1 per cent Corbis Policies: Where the Greens stand on the major issues Wages National minimum wage to be lifted to living-wage levels and to reach £10 an hour by 2020. Would also “curb boardroom excesses” by linking salaries at the top of companies to pay at the bottom Getty Policies: Where the Greens stand on the major issues Pensions End pensioner poverty by introducing a weekly “citizen’s pension” of £170 for a single person and £300 for a couple Getty Policies: Where the Greens stand on the major issues Energy Targets and timetables for improving efficiency and reducing greenhouse-gas emissions across all sectors. Wants electricity use to be reduced by a third by 2020, by half by 2030 and two-thirds by 2050 REX FEATURES Policies: Where the Greens stand on the major issues Health Accuses Labour and Tory governments of introducing privatisation by stealth into the NHS. Pledges to “maintain a publicly funded, publicly provided health service” Getty Policies: Where the Greens stand on the major issues Education Money would be allocated to schools according to their needs rather than their status. Schools which remain in the private sector would be classed as businesses, have all charitable status removed and pay taxes Getty Policies: Where the Greens stand on the major issues Railways Bring railway network back into public hands as franchises expire or if companies break the terms of their agreements Getty Policies: Where the Greens stand on the major issues Immigration Rules would be “based on the principle of fair and prompt treatment of applicants rather than on excluding dishonest applicants whatever the cost to the honest ones” Getty Images Policies: Where the Greens stand on the major issues Food Minimise transport of food and other agricultural products by supporting local food distribution and pressing for transport costs, especially air freight, to fully reflect environmental impact Creative Commons Policies: Where the Greens stand on the major issues Farming Phase out all “factory farming” and support a transition to small, free-range units, mixed rotational farming and extensive grazing. Would ban battery farming of poultry Getty Policies: Where the Greens stand on the major issues Genetic engineering Moratorium on the release of genetically modified organisms (GMOs) into the environment and on the importation of food and feed containing GMOs, pending comprehensive assessment of the technology’s safety Getty Policies: Where the Greens stand on the major issues Cannabis Possession, trade and cultivation of cannabis would be immediately decriminalised. Trade in cannabis would be examined by a Royal Commission, with a view to establishing a fully legalised and regulated trade Reuters Policies: Where the Greens stand on the major issues Housing Reform housing benefit to give greater help to poorer tenants and to prevent eviction or repossession of either private tenants or homeowners Getty

“Over the past 4 years I've become ever more aware that the challenges facing my constituents in Brighton can only be fully addressed by completely changing not just the damaging policies of this Government, but the way we do politics itself. That's why our bid for leadership is centred on going beyond politics as usual.”

Mr Bartley said the Greens could stand down in a “handful” of seats in exchange for political reform but only if local parties agreed the move.

“The one-off 2020 progressive pacts we're talking about must be done on a case by case basis, as agreed by local parties – and will have at its core a commitment to a fair voting system,” he said.

“If it happened it would only be in a handful of seats – but it could make all the difference. Time is up for the two-party system – we want to seize this moment to create a new kind of politics.”

Mr Bartley stood in South London’s Streatham constituency in 2015, gaining around 9 per cent of the vote – up 7.1 per cent.

Ms Lucas is the MP for Brighton Pavilion. She was first elected in 2010 but in 2015 increased her majority to around 8,000 votes.

Green Party leaders are elected on two year terms. The post was created in 2007; before that point the party had two “principal speakers”, one man and one woman.