Forces have not agreed common specifications for many types of goods and services, which reduces their ability to make savings, said the National Audit Office (NAO).
Police forces are wasting time and money by over-complicating the purchase of the most common of items, such as high visibility vests, the spending watchdog says.
The watchdog found up to 20 different specifications among the 43 forces in England and Wales for high visibility vests, with some forces paying up to £100 for the item, while others only spent £20.
Police funding from the Government will have been slashed by £2.1 billion by 2015, of which forces are planning to achieve around a quarter or £550 million on procurement of goods and services from uniforms and police vehicles to estate and facilities management services such as cleaning.
Margaret Hodge MP, chair of the House of Commons Public Accounts Committee, said: "It is unbelievable that something as simple as a high-visibility jacket has 20 different specifications, with associated prices that differ by as much as £80. Instead of focusing money on tackling crime, police forces are wasting resources disagreeing over how many pockets they should have on their uniforms."
The Home Office oversees the police service, and central government provides most of its funding, but individual forces have traditionally bought many goods and services independently. Many forces are now working with others to improve their buying power and make administrative savings, but most collaborations involve few forces and nearly half of all forces still have independent procurement teams.
Some forces have set up regional or national approaches to purchase common goods and services. However, common specifications for many types of goods and services do not exist, the NAO said, which reduces scope for collaborative buying. The NAO found at least nine separate specifications for each of five common types of equipment used by police officers, such as boots, body armour and the high-visibility jackets.
Policing and criminal justice minister Damian Green said: "The NAO report recognises progress is being made. The police are already required to buy vehicles, body armour and some IT through national agreements and we estimate forces will have saved £110 million by March 2013 through better procurement.
"We recognise there is more that can be done. That is why we are implementing a central online market place for the police to buy goods and services, saving money by purchasing together and from standard catalogues.
"Decisions about how best to make savings are primarily local and police and crime commissioners have a public mandate and a statutory duty to secure and maintain an efficient and effective force."