Upvote:4
It was overall a strategic general decision, a decision of quality vs quantity, and what was needed was quantity. The preliminary bombardment at Somme used over 1.5 million shells.
The Shell Crisis of 1915 did generate quote a political scandal, so that was important for something like that not to happen again. No-one wanted a shortage.
The Munitions of War Act in 1915 ended the shell crisis and guaranteed a supply of munitions that the Germans were unable to match. That was the actual point: make a lot more munitions, no matter the quality. A sudden large increase in produced quantity will inevitably lead to lower quality.
Responsible for oversight and co-ordination of the production and distribution of munitions for the war effort was the Minister of Munitions.
So you can in theory blame minister David Lloyd George for the quality (who led the Ministry of Munitions). Note that he was actually replaced on 9 July 1916. But from a neutral perspective there can be no blame of poor quality because the objective of the Ministry was purely quantity.