MPs from all three political parties in the Thames Valley have written to the prime minister urging him to ensure the killers of PC Andrew Harper remain behind bars.

The 13 politicians welcomed Andy Burnham's public opposition to the release of Jessie Cole and Albert Bowers but say those who kill an emergency worker while committing a crime should be excluded from an early release scheme aimed at easing prison overcrowding.

Harper, 28, died in 2019 when he was dragged behind the getaway car of three teenagers carrying out a quad bike theft in Berkshire.

Burnham says he shares public concern about the potential early release of those involved and "will not accept it's impossible to do more".

Signatories on the letter include Freddie Van Mierlo MP, whose constituency includes Harper's home town of Wallingford, Oxfordshire; Layla Moran MP, who represents Abingdon, Oxfordshire - where Harper had been based at a traffic unit; and former minister Olivia Bailey, MP for Reading West and Mid Berkshire.

Van Mierlo said PC Harper's "terrible death was felt most keenly by our constituents, and I know just how much hurt the potential for their release is causing".

The letter was sent on the same day 50 police chiefs sent a letter to Burnham saying he must pursue "every legal option" to prevent the early release of Harper's killers.

Under changes to the Sentencing Act made this year, Cole and Bowers, who were sentenced to 13 years for manslaughter in 2020, will become eligible for release in January after serving half of their sentences.

They are in a category of prisoners who until now would have had to serve at least two-thirds of their sentence before being considered for release.

A third man jailed for manslaughter - the vehicle driver Henry Long - was given a longer 16-year jail term and cannot be considered for the new early release conditions.

The MPs' letter tells the prime minister that PC Harper was "much loved" in the area, growing up in Wallingford, attending Henley college before taking a role in the police at the Abingdon traffic unit and attending incidents across the Thames Valley.

It also says emergency services must feel they have the "full backing of the politicians and public when they put themselves in danger".

The full list of signatories are:

Burnham has already asked his justice secretary to fast-track a plan for presentation to Parliament early next month to create more "headroom" in the prison system.

But he added it was "simply not possible to prevent all offenders from being released early without the prison system collapsing".