The Labour party are losing votes to the Greens and they don't seem to know what to do about it.

Until now, Ed Miliband's hopes of winning the next election relied upon holding onto a coalition of core Labour supporters, former Lib Dems and previously disaffected Labour sympathisers.

However recent polls have shown this coalition is splintering, with left-wing voters increasingly switching their allegiance to the Greens instead. Realising the threat this poses, Miliband tasked shadow Justice secretary Sadiq Khan with the job of winning them back.

Khan and his anti-Green strategy unit immediately set out their approach in a series of articles and blog posts earlier this year. Their approach was essentially a "good cop, bad cop" strategy. The good cop strategy was to convince Green voters that Labour had moved to the left since 2010. The bad cop strategy was to attack what they described as the Green's "disastrous" record in Brighton.

Neither strategy appears to be working.

Since Khan first reached out to Green voters, support for the Green party has actually gone up. The most recent Ipsos-Mori poll found the Greens on their highest ever share with the pollster, while other firms have repeatedly recorded the Greens polling ahead of the Lib Dems.

Claims of the Green's "deep unpopularity" in Brighton have also failed to hold up.

In several articles Khan and others attacked what he described as the "failed Green experiment in Brighton" which had left the party "deeply unpopular with local people". Labour's Luke Akehurst went even further, claiming the party's record showed them to be "extremists" who "were not a welcome addition to the UK’s political spectrum".

So what has happened since then?

Well earlier this year Lord Ashcroft conducted a constituency poll of the Green's only parliamentary seat in Brighton Pavilion currently held by Caroline Lucas. That poll found Labour slightly ahead of the Greens by one point.

Last month Lord Ashcroft polled the constituency again. This poll found the Greens were now a remarkable ten points ahead.

The details are even worse for Labour. Back in June, Ashcroft found that just 14% of Labour's 2010 voters were now voting Green. His latest poll reveals that number has almost doubled to 27%.

In order to see why this has happened we must look at how the Tories have failed to fight off the threat from their own smaller rivals.

Faced with rising support for Ukip, the Tories first dismissed their rivals, then tried to attack them as extremists and finally tried to mimic their policies. All of these strategies have backfired and Ukip's vote has continued to rise.

Now Labour seem to be making exactly the same mistakes with the Greens. Rather than take a consistent approach to appealing to Green-inclined voters, Labour have instead been all over the place.

On the one hand they have people like Sadiq Khan boasting about Labour's green record, and on the other hand they have Michael Dugher attacking the government for not spending enough on new roads. And on the one hand they have Khan claiming Labour have moved to the left, and on the other they have Ed Balls saying Labour will cut the deficit just as much as the coalition.

It is this basic inconsistency which is the root cause of Labour's problems and explains why so many of their former supporters are now being attracted to the Greens.

Earlier this year I had a chat with a figure close to Labour's anti-Green unit. They assured me that most Green voters "do not really care about the environment" and insisted that Labour were confident their policies on inequality would easily win them back into the fold

Several months on and that confidence seems to have been seriously misplaced.