Like one of those drawn-out celebrity divorces, the relationship between the Labour Party and the Co-Op continues to deteriorate. Every spat, every heart-rending denial of the love they once had for one another is played out in public.

Today it’s reported that Labour are planning to leave the Co-Op Bank – though it looks like a case of jumping before being pushed.

After the bank’s financial troubles (not to mention its crystal meth-addled chairman troubles) its new owners understandably have little interest in propping up a left wing party through unusually generous lines of credit. As I wrote back in October, the bank now intends to focus on commercial reality, rather than putting politics before the sustainability of the business.

Guido notes that Labour’s intended new bank, Unity Trust, is controlled by a combination of the Co-Op and the unions. They seem to be hoping to use Unity Trust’s “social mission” as a justification for securing yet more credit to stave off bankruptcy – essentially repeating the same dysfunctional relationship as before, in the hope that their new partner will put up with behaviour their ex won’t accept any more.

All of this is bad news for Ed Miliband’s election machine. True to their national record, the Labour party itself is laden with debt, and its fund-raising attempts have brought in less money than they hoped.

Already reliant on the unions for money, a move to Unity Trust will only increase union bosses’ power over Miliband.

It’s only going to get worse. The Co-Op Group, another major source of money for Labour, is now engulfed in its own commercial and reputational crisis. How long before the Group, following the Bank, stops trying to justify handing money to a political party when it should be getting its own house in order?