Harman is the Solicitor General, a subordinate of the Attorney General. The Attorney General is in charge of the CPS.
It isn't clear why such people should be involved in law making, as they have responsibilities for law enforcement. Also it isn't clear if this change is being introduced by public demand. Or if it is just Harman's idea.
Perhaps Harman was acting in her role as an MP, but the press article below describes her as Solicitor General.
Killers to lose 'I was provoked' defence By Rachel Sylvester
(Daily Telegraph, Filed: 03/03/2003)
The Government is considering removing the centuries-old defence of provocation in murder cases.
Harriet Harman, the Solicitor General, says in an interview with The Daily Telegraph, that the law, "from a previous age", should be changed. "It blames the victim," she says. "Men say, 'The woman wound me up; she was planning to leave me and I was upset and therefore I am not guilty of murder.' Even if a woman has done all of those things it does not justify violence, let alone violence to the point of death." There are about two domestic homicides every week, 95 per cent of them by men, and Miss Harman believes that the killers are getting off too lightly. Men who say they were provoked into killing their wives are usually convicted of manslaughter rather than murder. The Government is considering changing the 1957 Homicide Act to make it impossible to use provocation as a defence. Guidance is be given to prosecutors that domestic homicides should carry a charge of murder, not manslaughter.
The proposed change would affect other situations as well. For example, if a young man was being racially taunted and lashed out, killing the abuser, he would no longer be able to mount a defence based on provocation. Miss Harman is considering creating a new form of defence that would allow women who kill their husbands after years of physical abuse to be treated more leniently. Domestic violence victims would also be given the right to anonymity
Acknowledgement : article from The Daily Telegraph of 3 Mar 2003.