The schemes, which are expected to lead to the introduction of a nationwide system, are aimed particularly at policewomen who want to combine families with maintaining their careers.
The Home Office announcement follows strong lobbying from some reformist quarters of the police and concern that British regulations were out of step with EC equal opportunities legislation. It brings the police service into line with the Civil Service.
Officers up to the rank of chief inspector will be able to work a minimum of 16 hours - two days or two shifts for patrolling officers - a week.
The Home Office said it would be up to individual chief officers to decide whether any particular job could be accomplished on a part-time basis or whether the person would have to be offered another posting. But part-time officers would not automatically be confined to backroom roles.
Officers of superintendent rank and above, who act as managers, will be allowed to work part-time only on the basis of shared jobs, to ensure consistency of experience.
The scheme begins in the Metropolitan Police and Cleveland today with West Midlands, Norfolk, Nottinghamshire and Thames Valley starting later in the year.
Behind the scheme is growing concern at the loss of highly trained policewomen who are unable to return to full-time work after maternity leave. Many have been trained in skills such as sexual and child abuse counselling.
Officers studying for degrees or other qualifications may also wish to work part-time.
Speaking on BBC Radio yesterday, Kenneth Clarke, the Home Secretary said: 'I think it will spread quite rapidly, because I think enlightened employers nowadays introduce measures of this kind to get the best out of the workforce.
'It is part of making the police an employment like any other, bringing them into line with good management practices, making sure we bring forward women alongside their male colleagues in the force.'
Joanna Foster, chair of the Equal Opportunities Commission, said: 'All too often in the past women have achieved rank in the police at the expense of a family - now they will be able to combine work and a family.'