When I asked Sir Keir Starmer a couple of weeks back if he was ruthless, he said he was – but qualified it.

His ruthlessness was trained firmly on trying to get a Labour government that “could change this country for the better”.

He was “not ruthless for [his] own ambition”, nor was it ruthlessness for the Labour Party.

“I’m ruthless for the county,” said Sir Keir. “The only way we’ll bring about change in the country is if we are ruthless about wining the general election.”

But that ruthlessness is now blowing up and knocking the party’s election campaign off course.

Politics live: Another Conservative defects to Labour

After a slick first week, Labour is having its first crisis, as the row whether to de-select Diane Abbott has seized the headlines and muddied the message.

It has prompted, not just open splits at the top of the party, but wider questions about whether Starmer is purging the Labour Party as left wing candidates are blocked from standing and loyalists are being drafted into safe sets.

Ms Abbott herself has called it a purge, while Andrew Fisher, who worked in Jeremy Corbyn’s team asked: “Is it racism, sexism, factionalism or a combination of all? Either way it looks appalling.”

After iron tight discipline, the party is beginning to fray at the edges.

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Ms Rayner, the most senior women in the party, came to Ms Abbott’s defence today, telling me in the Sky News daily podcast that she should be allowed to stand if that is what she would like to do.

Yvette Cooper has also weighed in, describing Ms Abbott as a trailblazer and a “really important figure in the Labour party”.

Starmer, for his part, says the decision hasn’t been taken and will be made by the party’s national executive committee.

But there is clear a split – and it looks ill-disciplined at exactly the time when the party needs to show the public that is not another version of the warring Tories.

Ms Rayner was careful not to lay the blame of this at the feet of Starmer. She told me when I asked if the party leader was trying to purge the left that she “didn’t think Keir was acting in a factional way” – but that doesn’t mean others are not.

When I asked her about what Andrew Fisher had said about this being a very bad look for the party, Ms Rayner said: “It’s not a great look the way Diane was briefed against.”

The briefings the The Times newspaper on Thursday night that Ms Abbott was going to be barred from standing, promoting her defiant response and a rally outside Hackney Town Hall, has taken the issue from being relatively contained to out of control.

And this is the dilemma for Starmer. If he is ruthless about changing Britain, the less left wing firebrands on this benches, the better.

If he only wins a small majority, he needs the support of all his MPs and can ill-afford a left faction frustrating his government. So de-selecting unbiddable MPs and replacing them with loyalists makes perfect ruthless sense.

But when does being ruthless tip over into something more sinister, that seems unfair and actually turns voters off?

Perhaps the Labour high command think they can ride it out, purge these MPs and the news cycle moves on.

But the party already has a big problem in what are supposedly safe seats with the Muslim community that are angry over their stance over the Israel-Hamas war.

They are also facing an independent Jeremy Corbyn in Islington North.

Does the party really want to kick out the first ever black woman MP from the party too?

One senior Labour figure insists to me that his is not a purge and that it’s “important” to see all these cases differently.

But even if that is the intention, it is not how it’s being received amongst big chunks of Labour backers and voters.

If Sir Keir Starmer is really ruthless about winning this election, he might be advised to resolve this issue and quickly.

As Rayner acknowledged, it has become a distraction and that will be – in her words – a “frustration” to Starmer.

His top team have long said they will have wobbles along the way and what’s important is how its handled. This one needs sorting, and quick.