The shadow justice secretary is accusing Boris Johnson of misleading the Commons at Prime Minister's Questions, when he claimed the government had implemented 16 recommendations from his review into the treatment of ethnic minorities in the criminal justice system.
In a letter to the prime minister - seen by the BBC - David Lammy urges Mr Johnson to correct what he calls "a catalogue of falsehoods" - and says only six of those 16 recommendations have been implemented.
Mr Lammy was asked by former Conservative prime minister David Cameron to carry out an independent review into the treatment of people from black, Asian and minority ethnic communities by the criminal justice system in England and Wales.
His report, published in September 2017, contained 35 recommendations.
During Prime Minister's Questions on Wednesday, Boris Johnson said: "Sixteen of the Lammy recommendations have been implemented. A further 17 are in progress; two of them we are not progressing."
Earlier this week, Justice Minister Alex Chalk answered a written parliamentary question saying 16 had been "completed", 17 were still in progress and two were not being taken forward.
In his letter, Mr Lammy says he presumes the prime minister was referring to the same 16 - but says of those, only six have actually been implemented.
They include the Ministry of Justice (MoJ) publishing all datasets held on ethnicity, the MoJ and Parole Board reporting on the proportion of prisoners released by offence and ethnicity, as well as the proportion of each ethnicity who go on to reoffend, and the Youth Justice Board publishing an evaluation of a trial of its 'disproportionality toolkit'.
But Mr Lammy says there are clear examples of measures that have not been implemented - such as the publication of all sentencing remarks in Crown Court in audio or written form, and the renaming of youth offender panels.
He writes that if the government is serious about correcting injustices, "it needs to be honest about the actions it has taken".
He says the effect of Mr Johnson's comments was that the House was misled - a breach of parliamentary rules - and says he must correct the record.
The letter is copied to the Speaker.
A Ministry of Justice spokesperson said: "We set out our action plan in response to the Lammy Review in December 2017.
"We have completed the actions we committed to for 16 of the recommendations, and actions for a further 17 will be completed within 12 months."
Downing Street has been approached for a comment.