In an audacious new election strategy, Labour is set to embrace Gordon Brown's reputation for anger and physical aggression, presenting the prime minister as a hard man, unafraid of confrontation, who is willing to take on David Cameron in "a bare-knuckle fistfight for the future of Britain", the Guardian has learned.

Following months of allegations about Brown's explosive outbursts and bullying, Downing Street will seize the initiative this week with a national billboard campaign portraying him as "a sort of Dirty Harry figure", in the words of a senior aide. One poster shows a glowering Brown alongside the caption "Step outside, posh boy," while another asks "Do you want some of this?"

Brown aides had worried that his reputation for volatility might torpedo Labour's hopes of re-election, but recent internal polls suggest that, on the contrary, stories of Brown's testosterone-fuelled eruptions have been almost entirely responsible for a recent recovery in the party's popularity. As a result, the aide said, Labour was "going all in", staking the election on the hope that voters will be drawn to an alpha-male personality who "is prepared to pummel, punch or even headbutt the British economy into a new era of jobs and prosperity".

Strategists are even understood to be considering engineering a high-profile incident of violence on the campaign trail, and are in urgent consultations on the matter with John Prescott, whose public image improved in 2001 after he punched an egg-throwing protester.

Possible confrontations under discussion include pushing Andrew Marr out of the way while passing him on a staircase, or thumping the back of Jeremy Paxman's chair so hard that he flinches in shock.

One tactic being discussed involves provoking a physical confrontation at one of the three ground-breaking TV debates between the candidates. In this scenario, Brown, instead of responding to a point made by Cameron, would walk over from his microphone with an exaggerated silent display of self-control, bring his face to within an inch of the Tory leader's, and in a subdued voice, ask "what did you just say?", before delivering a single well-aimed blow to his opponent's face, followed by a headlock if required.

The bloodied and bruised Cameron could then be whisked to a nearby hospital, where a previously briefed team of doctors and nurses would demonstrate the efficiency and compassion of the NHS under a Labour government.

Saatchi & Saatchi, the agency behind the poster campaign, are also considering reworked posters from classic movies, casting Brown as The Gordfather, the Terminator, and "Mr Brown" from Reservoir Dogs, or perhaps linking him to Omar Little, the merciless killer in the TV series The Wire, in order to burnish the prime minister's "gangsta" credentials. Another set of designs appropriates the current Conservative anti-Brown poster campaign, employing adapted slogans such as: "I took billions from pensions. Wanna make something of it?"

The Brown team has been buoyed by focus group results suggesting that an outbreak of physical fighting during the campaign, preferably involving bloodshed and broken limbs, could re-engage an electorate increasingly apathetic about politics. They also hope they can exploit the so-called "Putin effect", and are said to be exploring opportunities for Brown to be photographed killing a wild animal, though advisers have recommended that weather, and other considerations, mean Brown should not remove his shirt.

Labour further hopes to "harness the power of internet folksourcing", the aide explained, encouraging supporters to design their own posters, which could then be showcased online. The "design your own poster" initiative has caught the imagination of Downing Street strategists, the aide said, because it is cheap, fosters engagement among voters and, above all, nothing could possibly go wrong with it.

For their part, Conservative strategists are said to be troubled by internal research suggesting that several members of the shadow cabinet – including Cameron and George Osborne – would in fact not "come here and say that" if challenged by Brown, instead turning pale and running away, or arranging for an older brother to wait outside the Houses of Parliament to attack him when he is least expecting it.