//Amanda Stretton, motoring editor of Confused.com says that drivers don’t realise that driving with an unrestrained pet which causes an accident can invalidate your car insurance, meaning you personally having to pay out for repairs in the event of a claim, and you may incur a fine of up to £5,000//
The she's wrong (at least as far as the insurance issue goes). If she had read the RTA S148 she would realise she was. There are very few grounds on which insurers can invalidate Third Party cover. S148 lists the grounds on which they may not (and in fact an EU directive goes even further than that but it need not worry us here). The list included in the RTA under which insurers cannot avoid cover is this:
(a) the age or physical or mental condition of persons driving the vehicle,
(b) the condition of the vehicle,
(c) the number of persons that the vehicle carries,
(d) the weight or physical characteristics of the goods that the vehicle carries,
(e) the time at which or the areas within which the vehicle is used,
(f) the horsepower or cylinder capacity or value of the vehicle,
(g) the carrying on the vehicle of any particular apparatus, or
(h) the carrying on the vehicle of any particular means of identification other than any means of identification required to be carried by or under the Vehicle Excise and Registration Act 1994.
Clearly an unrestrained dog would come under (d). An insurer may restrict payments under the "Own Damage" section of a comprehensive policy (if their Ts&Cs permit them to) but they cannot, by law, restrict cover for Third Party damage or injury.
Quite simply Ms Stretton is wrong and she is misleading her readers. But she's not alone because you frequently see publications which suggest something similar (the most usual being that having no valid MoT certificate will void your insurance. This is also incorrect. It will be covered by (b) above. In a test case about ten years or more ago an insurer argued that having no MoT did not relate to "the condition of the vehicle" and they were entitled to void a policy. They lost.