I just received a reponse from DC's office on my question about tax credits and this is what they said:
"If we win the next election, we will work with the tax credits system we inherit, but our first aim should be to make the system simpler and fairer.
At the moment, there are over a million people pretending to live apart because the benefit system pays you more to live apart than together. In a nutshell, the benefit system is driving people apart rather than bringing them together.
If we don't help couples stay together, if we don't build strong families, then what we get is family breakdown, which has huge social implications and also costs for the economy.
We will, therefore, end the couple penalty and recognise marriage in the benefits system, over time, by using savings generated from our radical programme of welfare reform."
So people pretending to be apart, but are not actually apart, are being driven apart by the benefits system