The mother of PC Andrew Harper has said her family is «paying the price» after the government confirmed that two of the men convicted of killing her son remain eligible for early release under revised plans to ease prison overcrowding.

Ministers have apologised to the Harper family over the scheme, which was redesigned after mounting pressure from MPs and victims. Prime Minister Andy Burnham announced changes to the early release policy, but the updated measures still leave some serious offenders, including killers and domestic abusers, within the eligibility criteria.

Under the sentencing changes, around 5,000 prisoners are expected to be released early. The government has said the policy is needed to tackle prison overcrowding, but the decision to keep killers and domestic abusers in the scheme has drawn criticism from MPs and from families affected by violent crime.

The Harper family's reaction came after it became clear that two of PC Harper's killers would still qualify for early release despite the prime minister's announcement. His mother said she was «bitterly disappointed» that the two men remained eligible. She said the family was «paying the price» for the policy, a reflection of the distress caused by repeated changes to sentencing rules.

PC Harper was killed in Berkshire. The case has become a focus of concern for those who argue that early release schemes should exclude violent offenders. His mother's comments have added to the pressure on ministers to justify the decision to leave two of his killers within the scope of the programme.

The government has apologised to the family for the pain caused by the scheme. It has said the revised policy is intended to reduce pressure on an overcrowded prison system.

The revised plan is narrower than the original proposal, but it does not go as far as some MPs and victims' families had urged. Domestic abusers and offenders convicted of killing will still be eligible for early release in certain circumstances, a point that has dominated the political reaction to the announcement.

The scheme is part of a wider attempt to manage a prison population that has been running at or near capacity for years. Ministers have faced repeated calls to take action, and the early release programme is one of the measures introduced in response. The eligibility of killers and domestic abusers has, however, remained a flashpoint for critics.

The scheme is expected to affect thousands of prisoners, with about 5,000 people due to be released early under the sentencing changes. The Harper family has indicated that the announcement does little to ease the pain of their loss, and their criticism has become part of the wider political debate over the policy.