The Home Office has been criticised by opposition MPs over a scheme to send hundreds of thousands of chicken boxes branded with #knifefree to chicken shops in an effort to dissuade young people from carrying the weapons.

Policing minister Kit Malthouse said on Wednesday that the chicken boxes would help emphasise the dangers of carrying a knife and challenge the idea that it makes you safer, but Labour MP David Lammy said the government was stereotyping black people.

“The Home Office is using taxpayers’ money to sponsor an age-old trope,” he told the Guardian. “Boris Johnson has already called black people ‘piccaninnies with watermelon smiles’. Now his government is pushing the stereotype that black people love fried chicken. This ridiculous stunt is either explicitly racist or, at best, unfathomably stupid.

“I know it might cost a bit more time, effort and money, but I would love it if you would announce a programme of investment in our local communities instead of spending five minutes on a harmful gimmick.”

Is this some kind of joke?! Why have you chosen chicken shops? What's next, #KnifeFree watermelons? https://t.co/34DwwxSmCN — David Lammy (@DavidLammy) August 14, 2019

The shadow home secretary, Diane Abbott, echoed Lammy’s criticism of the government.

“Instead of investing in a public health approach to violent crime, the Home Office have opted for yet another crude, offensive and probably expensive campaign,” she tweeted. “They would do better to invest in our communities not demonise them.”

More than 321,000 of the boxes are to replace the usual packaging at 210 chicken shop outlets including Morley’s, Dixy Chicken and Chicken Cottage in England and Wales, following a pilot at 15 branches of Morley’s in March.

Stories about young people who pursued boxing and music, rather than carrying a knife, will also be printed inside the boxes.

The #knifefree campaign will be shown on screens in many of the shops, with the adverts having already been shown at music festivals Wireless and Lovebox this summer. It will also be running at Notting Hill carnival.

Malthouse said: “These chicken boxes will bring home to thousands of young people the tragic consequences of carrying a knife and challenge the idea that it makes you safer.

“The government is doing everything it can to tackle the senseless violence that is traumatising communities and claiming too many young lives, including bolstering the police’s ranks with 20,000 new police officers on our streets.”

Morley’s managing director, Shan Selvendran, said: “Morley’s are proud to support the #knifefree campaign. We have been saddened by the recent increase in knife crime. We want to promote being knife free by using custom chicken boxes to deliver the message and start conversations amongst all of our customers.”

On a Facebook live stream on Wednesday, Johnson appeared to endorse people from ethnic minorities being targeted by police conducting stop and searches.

Abbott said “discriminatory” searches were “a reckless disregard for civil rights” and highlighted how the rise in violent crime came after cuts to policing, education and youth and mental health services by Conservative-led governments since 2010.