The proposed changes are expected to be laid out in the Queen's Speech
A judge has criticised plans to prevent men using the sexual infidelity of their partners as grounds for a defence of provocation in murder cases.
Lord Phillips of Worth Matravers, the head of Britain's highest court, said he was "uneasy" about the proposals.
He said it was wrong to prevent infidelity being looked at even as possibly "amounting to provocation".
Details of the proposed legal changes for England and Wales are expected in the Queen's Speech.
As things currently stand, men or women who argue that the infidelity of their partners provoked them to kill can enter a provocation plea which allows them to be tried for manslaughter instead of murder.
'Culture of excuses'
But speaking to lawyers at the firm Clifford Chance, the judge said the proposed legislation would say that "an act of sexual infidelity is not, of itself, an exceptional happening".
He said that at present the law requires "provocation to be conduct that would cause a reasonable man to act as the defendant acted".
Lord Phillips, who is the senior law lord, said he was also concerned about other aspects of the proposed changes, saying they would add a level of complexity to "the summing-up and raise difficulties for the jury".
When the proposed shake-up of murder laws were announced earlier in the year, Harriet Harman, Minister for Women, said: "For centuries the law has allowed men to escape a murder charge in domestic homicide cases by blaming the victim.
Lord Phillips says the government's proposals have left him "uneasy"
"Ending the provocation defence in cases of 'infidelity' is an important law change and will end the culture of excuses."
The judge's concerns have been described as "very worrying" by Women's Aid.
Spokeswoman Judith Stephenson said: "The current law allows men to get away with murder and places the blame on victims of domestic violence, rather than the perpetrators.
"Women's Aid wholeheartedly welcomes any measures that serve to reduce the inequalities experienced between men and women in this area where provocation defences are based on 'nagging', 'infidelity', jealousy or breach of so-called honour within their intimate relationships. "
A Ministry of Justice spokesman said the government welcomed Lord Phillips' comments and that they would be given due consideration.
He said: "The government is grateful to receive Lord Phillips' comments on the proposals contained in 'Murder, manslaughter and infanticide: proposals for reform of the law'."
The spokesman added: "The government plans to publish a summary of responses to the consultation within the next few weeks, together with an indication of how it intends to proceed in respect of reform of this area of the law."