‘Umar bin Al-Khattab used to prohibit anyone in the government from engaging in trade, whether they were selling or buying.
It was narrated that an agent of ‘Umar, al-Harith ibn Ka’b ibn Wahb, started to get rich, so ‘Umar asked him where his wealthh was coming from. Al-Harith replied: “I had some money and I engaged in trade with it.” ‘Umar said, “By Allah, we did not appoint you to engage in trade! ” and he took from his the profits that he had made.
Without the complete separation of government from business, there will always be conflict of interests, indeed, business will have the advantage over government, and decisions will be made to serve private business interests instead of responsible social policy.