“Tory sleaze is back” is Labour’s new mantra – a bold charge first laid down by Rachel Reeves as the party challenged the government to back a more wide-ranging inquiry into lobbying and cronyism after the Greensill saga. Labour has come to see it as the Conservatives’ biggest weakness, with one insider likening the drip-drip of cronyism allegations to those that engulfed John Major’s government. On Wednesday, Labour communications chiefs made the decision to move up a gear and start calling it “sleaze”, after six months of attacking the cronyism of government contracts and appointments during the pandemic. The party noticed voters bringing up cronyism in mid-2020. “There was a real discomfort with money for your mates, jobs for the boys,” one senior Labour source said. “It was really cutting through, people didn’t like it. They saw the dodgy contracts, the wastage, and they knew their money was being abused.” The strategy is now seen as so important for Labour that it is the main preoccupation of Reeves, Starmer’s closest shadow cabinet ally, who shadows Michael Gove at the Cabinet Office. There is also a useful comparison that can be made with Starmer, who is not a veteran of Westminster and comes from a legal background. The Labour leader looked at his most comfortable in weeks during a solid prime minister’s questions performance on Wednesday, where he laid out his record of prosecuting MPs who had broken expenses rules. “We really need now to move up a gear in how we present Keir as an alternative, how we draw on his record as a prosecutor and as someone who has come from outside politics,” one adviser said. “That’s what makes him the answer.” Cynics believe the affair may be too complicated to have real cut-through or electoral impact, that the public have already priced in some degree of “chumminess” with Boris Johnson, and that voters don’t discriminate between the parties when it comes to what they see as political corruption. But Labour chiefs believe there is a crucial difference between the fairness of how taxpayers’ money is treated and salacious stories about Johnson’s sex life, which the public barely bat an eye over. The former is what they will try to hammer home. “We cannot argue that Johnson is a bit Teflon, he has been for years. But there is something in this charge that might stick,” one senior adviser said. There are three big challenges for Labour. First is whether it can provoke enough public disgust. Are the public so jaded that they believe the revolving door from government to the private sector is just par for the course? The second challenge is whether it can drive this scandal through the door of 10 Downing Street and pin it to the current administration. It remains highly convenient for Johnson that David Cameron is the public face of the Greensill scandal. Judging by the mud-slinging against Cameron in parliament from the Tory benches, Johnson’s MPs are onboard with this fightback strategy. The civil service is also taking a good share of the flak with the revelation that a senior official, Bill Crothers, worked for Greensill while still in Whitehall, all approved by the Cabinet Office at the time. Johnson can so far just about get away with saying “nothing to do with me”. The third challenge is the complexity of the story: how Cameron’s chummy texts to Rishi Sunak relate to jobs at Liberty Steel. But one Labour source said it made little difference whether anyone could recall the name Bill Crothers in three months’ time. “This is a long game, what matters is that people who listen to music on the radio and hear the news bulletins, they hear ‘conservatives, lobbying, cronyism’ and that is beginning to bed in,” one Labour source said.