Keir Starmer has said he will “make absolutely zero apologies for being blunt” in an article published after a row over a widely criticised Labour attack advert on child sexual assaults. In a veiled message to critics within his own party, the Labour leader said he will “stand by every word Labour has said on this subject” and would continue to use the Conservatives’ record on crime as a legitimate criticism “no matter how squeamish it might make some feel”. The advert, which drew criticism from both left and right, used a picture of Rishi Sunak and said he “does not believe adults convicted of sexually assaulting children should go to prison” and pointed to the Conservative record on offenders avoiding jail. Several senior Labour figures distanced themselves from the poster. The Observer reported that the shadow home secretary, Yvette Cooper, “had nothing to do with it”. In an opinion piece for the Daily Mail, Starmer said Labour would continue to take on the Conservatives on law and order and pointed to the case of Zara Aleena, the aspiring young lawyer who was murdered by an offender who had been recalled to prison two days before the attack and should not have been free. “For the first time in my lifetime, everywhere you look – from the economy to the NHS to the chaos on our streets – we have been set on a path of decline,” Starmer said. He said the last decade had seen the UK “become a country where thugs, gangs and monsters mock our justice system and make decent people’s lives a misery”. Starmer said the party would be repeatedly calling out the Conservatives on uncomfortable issues. “When fewer than two in every 100 reported rapists see the inside of a courtroom, it means victims are being told their bravery means nothing by the Tories,” he wrote, citing statistics on burglary, court backlogs, fraud and fly-tipping. In comments aimed at some on the left of the party who have voiced concerns about the strategy, Starmer said: “Too many people treat this as trivial, unimportant or something Labour shouldn’t talk about. Working people suffer when crime is left unchallenged – crime will always be a Labour issue. “Try telling the people I meet who are scared to go out at night, because their communities suffer the brunt of failures to tackle crime, that law and order doesn’t matter. They will give you short shrift. “I make absolutely zero apologies for being blunt about this. I stand by every word Labour has said on the subject, no matter how squeamish it might make some feel. When 4,500 child abusers avoid prison, people don’t want more excuses from politicians – they want answers.” The piece comes after criticism from MPs in the party, including the former shadow chancellor, John McDonnell. But one of the most pointed criticisms came from David Blunkett, the former Labour home secretary, who said he had been left “close to despair” by what he described as a “deeply offensive” advert, which he said marked a descent into “gutter” politics. In a comment piece for the Mail, he wrote: “Once you resort to personal abuse, you create the risk that Britain’s public discourse will degenerate even further – to the levels that we have seen recently in the US. “When baseless allegations and spurious slurs replace fair and robust political debate, not only is the standing of our leaders undermined, the very foundations of our democracy are compromised.” Blunkett said he found it “impossible to believe” that Starmer “would endorse publishing this kind of material during a local election campaign”. The advert was part of a series on the Tory record on crime after a push on law and order campaigning last week. Starmer and the shadow chancellor, Rachel Reeves, will move the campaign on to the economy and the cost of living this week.