David Cameron has apologised for not spelling out the proposed changes to child benefits in his party's election manifesto.
Political editor Nick Robinson reports that the details of the child benefit cut and married couple tax break were only decided "very, very late".
"The wrinkles, at least in the presentation about the policy, were not really ironed out," he said.
John Whiting, of the Chartered Institute of Taxation, told the programme that the tax policy looked like it "wasn't thought through".
He explained how a "fault-line" ran through tax policy, between single and family income, which created "all sorts of anomalies".
"The fairer you try to be, the more complex you are," he said.
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