By Isla Binnie and Kate Abnett MADRID/BRUSSELS (Reuters) – European countries and companies could end up defining their own standards on green investments if Brussels fails to impose the “gold standard” and classifies spending on gas and nuclear energy as sustainable, a Spanish minister said on Wednesday. The European Union has split opinion among member states with its plan to include gas and nuclear plants – provided they meet certain criteria – in its sustainable finance taxonomy, a rulebook of investments that limits which can be labelled as green. “I guess that we will have a silver stand…