It's become a cliche to bemoan the fact that politicians are disproportionately Oxford PPEists. This is odd, as there's not much evidence that they read much E. Here are seven basic principles of economics that don't seem to be wholly grasped by the main parties.
1. Tax incidence. The burden of a tax doesn't necessarily fall upon the people who hand over the money. For example, stamp duty helps to lower house prices - which means that Labour's proposed cut for first-time buyers might just raise prices and so not help FTBers much. Similarly, a Mansion Tax would reduce the price of Mansions. That's a double blow for owners of mansions now, but it means that future owners won't be hurt; although they'll have to pay a tax, they'll buy their mansion cheaper. Also, in an open economy (pdf), it's likely that taxes on companies - in the form of a higher corporate rate or those unspecified anti-avoidance measures the parties like - will fall partly on labour insofar as the tax reduces investment.
However, incidence doesn't just matter for taxes. There's also benefit incidence. Housing benefit is in fact landlords' benefit because it raises rents. And welfare benefits help some firms as much as claimants: where do those benefits get spent?
2. Productivity growth matters. In the long run, it determines GDP growth. A party that was serious about wanting to improve living standards would therefore have a policy to raise productivity growth.
3. The knowledge problem. Any serious policy - in politics and in fact in life generally - must begin from the question: what do we really know? Politicians commonly overstate their knowledge. This leads to promises to cut government borrowing, even though this might not be feasible if economic growth slows. And it also closes off some interesting policy options such as the provisions of services through cooperatives rather than hierarchies.
4. The paradox of thrift. Efforts to save more or borrow less can be collectively self-defeating. To put this another way, falling government borrowing requires increased private sector debt. Oddly, the main parties don't seem keen to point this out.
5. Factor price equalization. Yes, foreigners might be forcing down British wages. But they don't need to migrate here to do so; international trade can bid down unskilled wages. The notion that immigration controls are sufficient to raise wages greatly is just wrong.
6. Deadweight costs.Labour wants to spend more on immigration controls.For a given (overly tight) fiscal policy, this is money and people diverted away from where they could do more good. That's a deadweight cost.
Another important deadweight cost is that of tax complexity; it leads to people looking for loopholes and gaming the system rather than doing proper work. Tax simplification (and benefit simplification too) should be a higher priority than it is.
7. Supply and demand. If you want to make houses more affordable, you do one thing: build more of them. Lefties might stress the importance of state action, righties the importance of liberalizing planning, Both, though, should agree that demand-side policies such as Help to Buy or cutting stamp duty are just daft.
I don't pretend this is an exhaustive list. I've confined myself to ideas on which economists broadly agree but which the main parties seem to reject. There is a big gap between politicians and economists.