Dodgy number plates have proven the Achilles’ heel of an alleged conspiracy to murder a prominent underworld figure and firebomb a vehicle.

Following a months-long investigation, police on Thursday arrested four western Sydney men and a teenager.

They are accused of being involved in a plot police allege included multiple staged vehicles, surveillance, getaway drivers and assassins.

The first sliver of evidence came in September when police stopped a BMW sedan sporting cloned number plates at Bankstown.

The driver sped away, leading officers on a chase through two suburbs. He allegedly evaded capture.

Police found the car abandoned about 40 minutes later, along with a loaded handgun thrown away on a nearby street.

On Thursday, after a six-month investigation, five warrants were executed across southern and south-western Sydne, with five arrests made.

Men aged 26 and 21 were charged with conspiring to murder the alleged organised crime figure.

Two others were charged over allegations they conducted surveillance on the target.

One was also charged with driving a stolen vehicle, as well as possessing unregistered and illegal firearms.

Three of the alleged plotters were denied bail to appear in local court on Friday. A fourth, who is only 17, was released on strict conditional bail to appear in children’s court on May 14.

The fifth man, 20, is accused of firebombing a car along with one of the conspirators in a separate incident.

He was granted bail to appear in local court on May 14.

-AAP