From the Institute for Government.
The UK economy is based on free market principles, and direct intervention of the kind suggested by the government is the exception rather than the rule.
Rules prevent politicians or officials from simply handing out support to whomever they choose, in order to protect the public purse from waste and corruption, and to maintain fair competition in the economy. Intervention, when it does occur, should not be ad hoc but based upon a clear rationale that reflects the aims intended, and with full awareness of the costs and policy pitfalls.
Government documents such as the The Green Book and Managing Public Money set out in more detail how policy must be developed in light of objective analysis, in pursuit of a clear rationale and within the delegated powers set by Parliament.