Come on, this is decades in the making. New Labour are as much to blame.
I Agree, both sides have had a hand in this. The country hasn't had a coherent energy policy for decades and we are now reaping the whirlwind as a result.
However, with that being said the Tories have been in power now for nearly 13 years and in that time have also continued to do nothing but "short-term-ism" and 0 energy planning. They cut back out gas reserves to basically 0, relying entirely on the "just in time" delivery model that capitalism love so much and now we're coming up short.
No matter which way you cut it, the Tories have had 13 years to attempt to reverse any damage caused by the last Labour government, but instead have chosen to give tax breaks to the rich, transfer more of the tax burden to the working class (Well, anyone on PAYE technically) and caused a significant portion of our NHS and care staff to leave the country due to their headlong pursuit of "The B-word".
So yes, both sides share some responsibility for our current situation, however I think it's more than reasonable to lay a greater portion of the blame at the Tories feet, since they have had almost 13 years to attempt to fix things and have instead made it far, far worse.