Scotland Yard is a force of "commuter cops" - with officers living as far away as Cornwall and the South of France, a new report claims.
The Policy Exchange think-tank argued that the trend makes it harder to deploy personnel in emergencies such as riots or terrorist attacks.
The study cited figures showing that as of September last year, of 18,179 Metropolitan Police borough officers - 8,896, or less than half, lived in the capital.
Policy Exchange said many travel in from the Home Counties, with Hertfordshire seen as a "bit of a police conclave" - while some were living "very far from London".
In one interview for the report it was suggested that some officers "live in the South of France because they work 14 days on in a row, so they work 14 days in a row and then they go home for the remaining two weeks of the month".
And one "experienced" officer told researchers: "Eleven years ago we sold and moved to Cornwall, which is where I live at the moment. I do not commute daily". She did compressed hours and had a London flat, the paper added.
Even when they are off-duty, police officers stabilise communities and deter criminals, the report said, adding: "Londoners would benefit from having more police officers as neighbours."
The "commuting cops" phenomenon was also said to be against the interests of policemen and women given the anti-social hours and the unpredictability of their work.
Officers interviewed spoke of having to sleep on the floor after they missed their last trains, according to the research by Policy Exchange's Capital City Foundation unit.
Its author, Glyn Gaskarth, said: "Having a police force that lives outside London affects the ability of the Met to mobilise sufficient numbers of officers to deal with terrorist incidents or civil disturbances."
Most officers interviewed said they would like to live in London if they could afford it and the think-tank outlined proposals it said would mean thousands more Met personnel would be able to live in the capital.
It recommended that the force should work with housing associations to convert underused police properties into housing for discounted sale to officers.
Scotland Yard should also provide low-interest loans and top-ups for officers' savings, the report suggested.
Met Police Deputy Commissioner Craig Mackey said: "We have tried and tested plans to allow us to respond at pace and effectively to a range of critical incidents and do not believe that these are in anyway jeopardised by the places officers currently live."
He welcomed the report, but added: "Having cut £600 million off our spending in the past five years and needing to find another £400 million in the years ahead, our financial and operational future depends on us realising the capital of our under-used estate and re-investing that money in frontline policing.
"It is unlikely, in this financial climate, that we can fund the financial support the report suggests."
The Met is keen to ensure officers and staff have a "strong connection" with the city they police, Mr Mackey said. In 2014 a residency criteria was introduced meaning that new recruits must have lived in London for at least three of the previous six years.
Mr Mackey added: "We also recognise that for those connections to be maintained, officers need to have access to affordable housing, but equally we do not believe we are best-placed, as a police service, to be a housing provider - this should be left to specialists in the field of affordable and key-worker housing whilst we concentrate on keeping our capital safe."