"Company parking spaces are an extremely precious asset, whether they're for directors, staff or probably more importantly, your customers. So when drivers choose to clog up your spaces when they have no intention of visiting your business, it's annoying and inconvenient."
Graham said many firms had resorted to using a clamping company as a deterrent, which had proved particularly successful.
"But as a direct result of some clampers operating in an over-zealous manner and clamping everything in sight, the Government has decided to introduce a new law - the Protection of Freedoms Bill.
"This will make it an offence to clamp vehicles, even if they are illegally parked on your company's land, and your directors will face a fine if you're found guilty of operating such a policy."
Graham said the new rules also made it an offence to block a vehicle in by parking behind it, so companies would have to consider other options to stop unwanted visitors using their parking spaces.
"If it's possible, fit a barrier - this could be a simple lockable pillar or a more sophisticated automatic arm. This is an excellent option as if someone sneaks into your car park while the barrier isn't in place, the new rules mean you can close the barrier and stop the vehicle leaving.
"Of course you will then still have the problem of the unwanted vehicle on your land, but it should act as a good deterrent to stop them parking there again."
If you display the appropriate notices, you can also set charges for parking without your consent, even if you don't have a barrier system.
"And if the driver escapes without paying, the new rules make the vehicle's keeper responsible so you can get their details from the DVLA and send them the bill - take a photo of the illegally parked vehicle too in case your claim is disputed."