elimination of leakage current

You will need to look at each separately and break up each circuit to find the individual component(s) which are causing the leakage. If the problem is faulty components good oh replace them but if it is design then you'll need to put on the ol' thinking cap.

but according to our battery manufacturer,the acceptable limit of leakage current is 25 mA for cars (for clock & electronic control units) and for trucks and commercial vehicles it is 0mA. So they have asked us to get it corrected in our trucks.

Either get a new battery manufacturer with a decent quality product or rip out the stereo. Most new diesel engine systems have engine control computers that must have a small keep-alive current as well. They are probably also tapped off that line as well so I seriously doubt you will be able to get it to zero. The sad fact of the matter is that the internal leakage of low quality batteries will probably be close to 5-10mA all by itself.

Also if the vehicle has an alarm system it will probably be wired into that circuit as well.

As Rorschach says, if there are presets on the radio, it is not 0 weather it is a commercial vehicle or not. May need exact specs on the equipment to see what the proper "idle current" is for each part. 130 ma seems a little high, but you need the specs to know. -- JHF

I have found out that once i remove the stereo connections,the leakage current drastically comes down to zero. So how can I eliminate this current with the stereo connected?will a relay work?if yes,how can it be connected?any other suggestions?

Revise your standard would be my suggestion. you are trying to solve a non-problem and spending valuable time and money and running the risk of breaking stuff to do so. Your battery supplier is a lunatic if you ask me (and you are).

Er, um, switch them off when not needed, perhaps?