Tony Blair says police mergers are "not off the agenda", but said it would not be "sensible" to force them on police.
The mergers were opposed by many forces
He spoke just days after the only two forces to be actively seeking a merger, Cumbria and Lancashire, said it would not be possible on cost grounds.
Tory leader David Cameron accused Mr Blair, at prime minister's questions, of "wasting police time" on the issue.
Earlier, Home Office minister Tony McNulty said "the definitive answer" to whether there will be mergers "is no".
The Home Office's plans for mergers had been opposed by many police forces, although ex-Home Secretary Charles Clarke said they were a key part of reforms.
THE PROPOSED FORCE MERGERS
Humberside, North Yorkshire, South Yorkshire and West Yorkshire
Derbyshire, Leicestershire, Lincolnshire, Northamptonshire and Nottinghamshire
Cambridgeshire, Norfolk, and Suffolk
Bedfordshire, Essex and Hertfordshire
Surrey and Sussex
West Midlands, Warwickshire, Staffordshire, West Mercia
All four Welsh police forces
But following the failure of the voluntary merger between Cumbria and Lancashire forces, Mr Cameron asked: "Will you now accept that forced mergers are certainly out of the question?"
Mr Blair said ministers had listened to representations, and added: "We don't believe it's sensible to force the merger.
"It is still important and will be important in parts of the country that there is either merger of forces or certainly a far better strategic capability that crosses border lines."
But Mr Cameron said: "The flagship of forced mergers has sunk without trace."
Earlier, Mr McNulty told police authority members that government powers to force mergers through would be retained "as a last resort".
In a speech to the Local Government Association Mr McNulty conceded the existing government timetable was "ambitious to say the least" and said there would be a rethink.
He said: "There is now the time, for local government, as well as police authorities, police forces themselves, and other interested parties to collectively tell us, in each and every region, how - if not this way - then what way?"
The government's merger plans could have seen the number of forces cut from 43 to as few as 17.