For the thief, electro-mechanical immobilisation is too much hassle to bypass, requires too much equipment and expertise and takes too long to steal and the thief will probably fail anyway. It’s easier to steal a machine not secured with Kosran.

Electric immobilisers are redundant on diesel engines. Plant thieves are professionals. They do not joy-ride stolen machines. They steal to order for money and export.

The Advertising Standards Authority (ASA) has upheld a complaint by Kubota about a Kosran advert in which the immobiliser manufacturer claimed Kubota's immobilisation system could be overcome in 90 seconds.

In its defence Kosran submitted a DVD showing a Kubota machine apparently being 'hot wired' in 74 seconds but the ASA dismissed this saying: "...there was no independent verification to show whether the immobiliser had been operating correctly or that the process shown was accurate of real-life conditions."

The ASA also partly upheld a complaint about a phrase in the advert ...Electronic immobilisers on plant - unbelievable price - unbelievable if it stops your plant being stolen! Kubota said its immobiliser was a standard fitment, came at no additional cost and it was unaware of any protected items being stolen.

For its part Kosran said no-cost was an 'unbelievable price' and its aim was to draw attention to the effectiveness of electronic immobilisers. It also highlighted police records that showed between October and December 2008 there were 926 items reported stolen in the UK, of which 62 were Kubota's.

While the ASA agreed the wording did not imply a high price for immobilisers, it said there was no evidence about how the 62 machines were stolen, adding: "...Kubota's electronic immobiliser was certified by Thatcham as a Category P2, which we understood was the generally accepted industry standard that meant that it could resist attack for 15 minutes."

The ASA said the advert must not appear again in its current form. It also told Kosran not to denigrate competitors in future and not to make claims without robust substantiation.

Richard Harrison, sales and marketing manager for Kubota UK said: "We're absolutely delighted we won our two major points. We were not happy to have our products unfairly denigrated in the press."

Kosran's chief executive officer Patrick Sheeran said: "We are not impressed by the ASA's diligence and technical expertise and are considering a judicial review."