MPs have called for some police forces to merge
The number of police officers has fallen in most forces in England and Wales, Home Office figures have shown.
Between March and September 2009, 26 out of 43 forces recorded a reduction in their ranks last year.
But overall officer numbers rose 583 to 144,353 after large increases in Essex, Thames Valley, West Midlands and the Metropolitan Police, which was up 763.
The figures came as MPs urged ministers to reconsider merging some smaller forces as a way of saving money.
Forces are having to make cutbacks in the face of financial pressures and many chief constables fear officer numbers will have to be further reduced.
Three forces - South Yorkshire, West Yorkshire and Avon and Somerset - lost more than 50 officers between March and September 2009.
But increases in other areas pushed the overall total for England and Wales up slightly by 0.4%.
The Liberal Democrats said the widespread fall in numbers was a "worrying sign" of future cuts.
Down in six out of 10 forces in England and Wales
Up overall by 0.4% to 144,353
Biggest falls in South Yorkshire, West Yorkshire and Avon and Somerset
Biggest growth in Essex, Thames Valley, West Midlands and the Met
Source: Home Office
"Instead of squandering billions on ID cards, the government should concentrate on getting more police officers out on the beat," home affairs spokesman Chris Huhne said.
"The Liberal Democrats are the only party committed to increasing police numbers of every area of the country. It is time for the other parties to come clean about their plans."
Home Secretary Alan Johnson insisted officer numbers remained "historically high".
"But it is not all about numbers, the force must carry on tackling crimes that matter most to the public and that is why the government has guaranteed funding to maintain frontline strength until 2013," he said.
"The increase in civilian staff is freeing up officers, allowing them to dedicate more time to protecting the public and keeping the country safe.
"Next year's police investment will go up to more than £9.7bn and it is for chief constables to spend it where it is most needed."
The Home Affairs committee urged the government to look again at merging some of the smaller forces.
The last attempt to do so was scrapped four years ago amid fears over costs.
But the MPs cited the example of Bedfordshire and Hertfordshire which it said could be merged for a one-off cost of £20m with resulting savings of almost £15m a year.
The report said: "We urge the government to consider how forces and authorities can be assisted with managing the up-front costs of reorganisation.
"The long-term financial benefits should make this area of investment a priority.