The number of call-outs of armed police has increased by more than 50% in a decade, figures show.
Armed police are having to deal with a growing number of incidents
In a Parliamentary answer, Home Office minister Tony McNulty said firearms were authorised for 18,891 incidents in England and Wales in 2005/6.
This compares with 12,379 incidents in 1996/7 - a rise of 53%.
Lib Dems said figures showed officers increasingly expect to be confronted by armed criminals. Earlier this month new gun crime laws were introduced.
In London, the number of times armed response units were deployed almost doubled from 2,439 to 4,711 between 1996/7 and 2005/6.
In the West Midlands it nearly quadrupled from 270 to 1,044 over the same period.
In recent months, there have been several high-profile incidents of gun and knife crime.
The killing of 11-year-old Rhys Jones outside a pub in the Croxteth area of Liverpool, in August, sparked outrage across the country, and led to increased calls for a crackdown on gun and knife crime.
Earlier this month, new legislation was brought in aimed at making punishments harsher and tightening restrictions on the ownership and sale of guns and knives.
At the time, Home Secretary Jacqui Smith said tackling gun and knife crime was a "top priority", and said weapons on the street would not be tolerated.
Responding to the latest figures, Jeremy Browne, home affairs spokesman for the Lib Dems, said: "Firearms offences used to be rare in Britain and we associated gun crime with America.
"Now it is a daily concern for millions of people in our country."
The underlying problem was the huge growth in the availability of guns in Britain, he said.
He called for proper enforcement of anti-gun laws and greater efforts to intercept smuggled firearms.
A Home Office spokesman said there had been a 13% fall in gun crime last year and it remained "a top priority".
He went on: "We introduced a mandatory minimum five year sentence in 2004 for possession of an illegal firearm.
"Earlier this year we introduced a new offence of using someone to mind a weapon and it is now an offence to sell, manufacture or import realistic imitation firearms."
The spokesman said that, while it has "long been that police should not generally be armed", chief officers "must decide the appropriate response to incidents and whether the deployment of armed officers is justified".