UK Labour has pulled the rug from under its former Scottish leader by refusing to fund any more of her defence in a legal action brought by the controversial blogger Stuart Campbell.

The move, which exposes Kezia Dugdale to potentially significant costs, has been seen by some of her fellow MSPs as a “betrayal” and “factionalism” by her pro-Corbyn enemies.

Mr Campbell, 50, who runs the nationalist Wings Over Scotland website from his home in Bath, is suing Ms Dugdale for £25,000 in a defamation action started last November.

It followed the Lothians MSP accusing him in her Daily Record column of making a homophobic remark about gay Scottish Secretary David Mundell.

Mr Campbell had said Mr Mundell’s son, the Tory MSP Oliver Mundell, was “the sort of public speaker that makes you wish his dad had embraced his homosexuality sooner".

In her column, Ms Dugdale said she was “shocked and appalled to see a pro-independence blogger's homophobic tweets” - Mr Campbell vigorously denies homophobia.

Until now, the UK labour party in London has bankrolled all of Ms Dugdale’s legal support, paying for a QC and an advocate to conduct her defence at Edinburgh Sheriff Court.

The costs so far are understand to be close to £100,000.

However, to the shock of Ms Dugdale and many other Labour MSPs, the UK party has now ended the arrangement, leaving Ms Dugdale to fend for herself.

Although the party will bear all of Ms Dugdale’s costs to date, it will not pay for any more legal counsel or any damages and costs if she loses.

It is understood UK Labour, which raised £56m last year, did not tell Ms Dugdale directly of its decision, but informed her lawyers that it was no longer standing behind her case.

Ms Dugdale, 37, who was Scottish Labour leader from 2015 to 2017, opposed Jeremy Corby becoming UK leader, earning the lasting resentment of his supporters, who now dominate the party apparatus.

As the publisher of Ms Dugdale’s column, it is understood the Daily Record may now supply Ms Dugdale with legal support for the rest of the case.

However any help would not extend to damages and costs if Mr Campbell won his case.

Earlier this month, Sheriff Kenneth McGowan refused Ms Dugdale’s request to have the action thrown out and agreed to proceed to an evidential hearing.

Ms Dugdale had been on the point of appealing that decision when UK Labour withdrew its support, forcing her to scramble to lodge the appeal.

Ms Dugdale’s spokesman said: “Given the principles on which it was founded - equality, fairness and justice - the UK Labour Party wholeheartedly committed to paying all legal costs associated with this case from start to finish.

“It is very much hoped that all promises will be kept.”

UK Labour said: “It would be inappropriate to comment on a live, ongoing legal case.”

Mr Campbell declined to comment.