Labour’s deputy leader has refused to endorse a controversial attack advert from the party, but said it had served its purpose by drawing attention to the government’s “failure” to crack down on crime. Angela Rayner claimed she had not shared the ad on social media since it was posted last week because she had been spending Easter with family, and denied it was because she was “holding her nose” owing to personal reservations. As political parties gear up for a narrative-defining set of local elections next month, the scrutiny over which shadow cabinet ministers have explicitly backed the ad is growing. Some frontbenchers have privately confessed they feel uncomfortable about the claim, released in a tweet by Labour last Thursday, that Rishi Sunak does not think convicted sexual abusers of children should go to prison. In a mock-up poster carrying the prime minister’s picture and signature, the ad cited official statistics showing that, since 2010, 4,500 adults convicted of sexually assaulting children under the age of 16 had served no prison time. Asked multiple times on Thursday morning whether she agreed with the ad, Rayner declined to give her full backing to it. She said the ad and other similar tweets focusing on gun crime and Sunak’s wife having been non-domiciled for tax purposes were “really hard-hitting”. “It has caught the public’s attention and that’s what our intention was,” Rayner told Sky News. She stressed Labour wanted to “ensure the public do see that the prime minister and the Conservatives for the last 13 years have failed to tackle serious crime and have let criminals off the hook”. Rayner added that it was “right that we highlight these issues”. Though Sunak has been in government only since January 2018 and an MP since May 2015, Labour’s ads have sought to tie him to what it calls the failures of the previous four Tory administrations. Rayner acknowledged the ads were controversial, saying she was “known not to hold my punches”, but defended targeting Sunak personally for letting criminals off the hook amid claims of a broken justice system. “The government is setting the framework for that and they’re responsible for it, and Rishi Sunak is the prime minister,” she added. Asked if she had not shared the advert because she was holding her nose owing to personal reservations about it, Rayner insisted: “Not at all, no. I just think that these are hard-hitting ads about the government’s failure on crime and I think it’s right that we highlight that.” Pressed on whether she would share the ads after the Easter break, Rayner quipped: “No one tells me what to tweet.” The Labour leader, Keir Starmer, defended the advert in a piece for the Daily Mail over the weekend. He said he would “make absolutely zero apologies for being blunt” and sent a veiled message to critics within his own party, by telling them he would “stand by every word Labour has said on this subject”. Starmer added that he would continue to use the Conservatives’ record on crime as a legitimate criticism “no matter how squeamish it might make some feel”. “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,” he wrote. “When 4,500 child abusers avoid prison, people don’t want more excuses from politicians – they want answers.”