Labour leader Ed Miliband must change course or he will be "choosing to lose" in next year's general election, a senior official of an influential left-of-centre thinktank has warned.

Marcus Roberts, deputy general secretary of the Labour-affiliated Fabian Society, called for a move away from "safety-first campaigning" to broaden Labour's appeal to blue-collar voters, warning that the party has a problem outside the M25.

Writing in the New Statesman magazine, Mr Roberts - who worked on Mr Miliband's leadership campaign in 2010 - said that with a year to go until the May 2015 election, Labour was currently "managing a declining poll lead". The party was now facing a critical moment when it must change or face losing next year.

"E d Miliband has a simple choice to make: the Labour leader can replay the 2010 general election and hope for a different result or he can change course and try for a majority," wrote Mr Roberts.

"The numbers suggest that Labour's present strategy of managing a declining poll lead must be altered. Equally, there is a moral case for reaching out to the blue-collar voters whom the party was originally founded to represent. Without change, Labour will be choosing to lose."

Mr Roberts said Labour faced a choice between "Minority Miliband" and "Majority Miliband".

"Minority Miliband is an approach that aims for a narrow appeal to existing Labour voters and some former Lib Dems," he said. "It hopes to squeak over the finishing line and sneak Ed Miliband into No 10 through the back door of an electoral system that could translate the loss of the popular vote into a win for a minority government.

"By contrast, Majority Miliband would shift from safety-first election campaigning and over-cautious politics to recapture the public's imagination. It would be a politics that listens to blue-collar concerns, takes action and roots itself in the community.

"A radical manifesto, a clearer stance on issues such as immigration and welfare and an embrace of movement politics will be key. T he choice is Ed's."