The force would be linked by radio to the local police station and would deal with vandalism and minor crime at bus stops, in parks and housing estates.
" Labour's record in office is quite frankly abysmal. Police numbers have fallen, violent crime has risen and most of those who actually reach jail go on to offend again within two years. "
Lib Dem leader Charles Kennedy revealed more details of the force at the party's morning news conference where he condemned Labour's record on crime as "abysmal".
Ahead of a day of campaigning on law and order, he also pledged 2,000 more police than Labour is promising and said politicians should not be involved in setting sentences.
The new force would have paid, uniformed officers run by local councils to act as a bridge between the community and the police.
Although they would not have the same powers of arrest as police constables, they would deter and detect crime in sensitive areas, the party believes.
"They will be the eyes and ears of the community," home affairs spokesman Simon Hughes told journalists.
Mr Kennedy attacked both Labour and the Conservatives for allowing crime to rise when they were in power.
"At the last election, Labour promised to be tough on crime and tough on the causes of crime after so many years of Tory failure," he said.
"But Labour's record in office is quite frankly abysmal. Police numbers have fallen, violent crime has risen and most of those who actually reach jail go on to offend again within two years."
He also highlighted the Conservatives' record, saying crime had doubled in the 18 years they were last in power, while John Major's tenure as prime minister had seen a drop of 500 in police numbers.
The Lib Dems said the 6,000 increase in police ranks was 2,000 more than was promised by Labour.
Labour and the Conservatives tried to talk tough but only the Lib Dems could offer "necessary and vital" commitments to tackling crime, said Mr Kennedy.
"That is a woeful track record and the Conservatives have got little to offer. They have no plans in their manifesto to add a single extra police officer."
Mr Kennedy added: "Because the victims of crime are so often overlooked by the criminal justice system we will give them and their families greater rights to be heard in court."
Mr Hughes said that criminals currently being sentenced to short terms in prison often receive no help when they are released and end up offending again.
Under a Lib Dem government, they would serve "community" sentences in which preventing future criminal behaviour would be a priority.