David Merritt, whose son Jack was one of two people killed by convicted terrorist Usman Khan on Friday, condemned the prime minister and Priti Patel, the home secretary, for using the attack as justification for a series of tougher criminal policies.
Mr Merritt suggested the Tories were using his son's death to promote "vile propaganda" and shared a tweet accusing Mr Johnson of trying to "make political gain from people's death in a terror incident".
Cambridge University graduate Jack Merritt, 25, worked for the Learning Together programme, which uses education to try to rehabilitate prisoners into the community.
Following the attack, the Conservatives vowed to toughen terror sentences and stop criminals entering the UK from the EU, and launched a crackdown on people convicted of terrorism offences who had been released early.
That prompted Mr Merritt to share a tweet by left-wing journalist and academic Ash Sarkar which said: "It's beyond disgusting that Boris Johnson, Priti Patel and newspapers like the [Daily] Mail are using Jack Merritt's death and image to promote an agenda he fought against all his life. He was a passionate believer in rehabilitation and transformative justice, not draconian sentencing."
He then retweeted a second post by Ms Sarkar which said: "Jack Merritt's family and loved ones have asked that rightwing newspapers and political parties not use his murder to advance reactionary demands. If you see it happening, call it out. They deserve so much better."
Mr Merritt also posted two front-page articles about the Conservatives' crackdown on released terror offenders, writing: "Don't use my son's death, and his and his colleague's photos - to promote your vile propaganda. Jack stood against everything you stand for - hatred, division, ignorance."
www.independent.co.uk/news/uk/politics/boris-johnson-london-bridge-terror-attack-jack-merritt-father-daily-mail-a9228886.html