Firefighters and police officers could have the same boss under a proposed overhaul of the relationship between emergency services.
Police and crime commissioners (PCCs) will be given the chance to assume control of overseeing fire services in their area under plans announced by the Government.
The elected officials will then be able to put in place a single "employer" led by a senior officer in charge of hiring all local fire and police personnel.
Unions attacked the proposals, while ministers say better collaboration will strengthen emergency services and deliver savings and benefits for the public.
New legislation will allow PCCs to take on the responsibility of the fire and rescue authority in their area "where a local case is made that it would be in the interests of economy, efficiency and effectiveness, or public safety".
A single employer could then be created under the PCC's governance and be led by a chief officer, who will need to be of chief constable rank.
Rules will be changed to allow fire service personnel to apply for the the role. Below that post, a senior fire officer would lead fire operations, while a deputy chief constable would be appointed to lead police activity.
A Government consultation setting out the proposals stressed that the distinction between operational policing and firefighting will be maintained.
A law that prevents a member of a police force from being a firefighter will remain, there is no intention to give firefighters the power of arrest and central government funding for the two services will remain separate.
Ministers claim the moves will improve efficiency and make it easier for the two services to share back office functions.
The reforms will also place fire, police and ambulance services under a statutory duty to consider opportunities for collaboration.
Matt Wrack, general secretary of the Fire Brigades Union (FBU), said there is "absolutely no case" for PCCs to take over fire and rescue services.
He said: "These are badly thought out proposals from a Government which couldn't care less about emergency services or those they employ.
"Police are law enforcers, while fire and rescue is a humanitarian service with a very different remit and culture."
Policing Minister Mike Penning said commissioners are accountable and "uniquely placed to improve the way the emergency services are delivered at a local level".
He added: "It simply doesn't make sense for emergency services to have different premises, different back offices and different IT systems when their work is so closely related and they often share the same boundaries."
Fire Minister Mark Francois said the number of fires is falling each year, adding: "We want to remove any bureaucratic barriers to joint working and allow local leaders to make the arrangements that work best for them."
David Lloyd, of the Association of Police and Crime Commissioners, said they supported the proposals while "recognising that for a range of reasons ... not every area will wish to pursue these new opportunities."
Lynne Owens and Giles York, of the National Police Chiefs' Council, said in a joint statement that they welcome "any opportunity to enable the blue light services to work more effectively together in the public interest".
Other changes in the proposals include enabling a PCC to be represented on their local fire and rescue authority in cases where they do not assume responsibility of the organisations; giving the Mayor of London direct responsibility for the fire and rescue service in the capital; and encouraging local ambulance NHS foundation trusts to consider having PCCs represented on their council of governors.
The proposals come days after separate plans to expand the role of unpaid police volunteers.
Will Riches, vice chairman of the Police Federation, said: "Call me cynical but it all feels like musical chairs here.
"What concerns us, as a profession that relies on continuity and resilience, is that all these plans point in one direction: toward ways to do things cheaper rather than better."