TENSIONS within the unique alliance running Scotland’s railways spilled into the open yesterday, as one of the two partners publicly attacked the other at a conference.

A director of the company which runs the ScotRail trains criticised Network Rail, which is in charge of the track, for “continually” disrupting passengers with late engineering works.

Dutch firm Abellio and Network Rail are meant to work in harmony in the ‘ScotRail Alliance’.

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However Charlotte Twyning, Director of Policy, Strategy and Communications for Abellio UK, took a swipe at her partner in the Alliance, likening it to a troubled marriage.

Her remarks came just minutes after SNP transport minister Humza Yousaf said he wanted the two sides to work more closely together “to achieve great things”, and on the same day the Alliance published its 249-point performance improvement plan.

Labour called on Mr Yousaf to “get a grip” of the situation.

In recent months, Abellio has been the subject of growing criticism over commuter delays and poor performance at ScotRail.

However 54 per cent of delays above three minutes last year were due to Network Rail.

As fellow speaker Jonathan Pugh, Head of Strategy & Planning Scotland at Network Rail, sat nearby, Ms Twyning told a rail conference in Edinburgh: “This is the first time an operating company in the UK has joined formally with Network Rail to run a franchise.

“We remain convinced that this marriage, our relationship with Network Rail as the infrastructure owner, is in the best long term interest of passengers.

“However relationships take a little bit of work. As things stand today, we are not satisfied the Alliance is working for passengers in the way that it could.”

She went on: “I don’t think it’s unreasonable to expect the Alliance to perform better.

“For us, that means working with what we’ve got to deliver the best service we can for passengers today until we get new trains. For Network Rail that means completing engineering works on time, to budget, with minimal disruption to passengers.

“It is not OK for people to be continually disrupted by late engineering works.

“Both ScotRail and Network Rail need to keep the passenger in mind at all times.”

Speaking next, Mr Pugh said: "We need to work in partnership to deliver a successful railway."

Earlier Mr Yousaf told the audience the Alliance promoted “a more integrated approach in the management and delivery of the railway in Scotland”

He said: “I’ve asked that that cementing of the relationship goes deeper and goes further because in collaboration we can achieve great things.”

Scottish Labour transport spokesman Neil Bibby said: “Passengers deserve better than a blame game within what is suppose to be an Alliance. The buck stops with the Transport Minister and it’s time for Humza Yousaf to get a grip and sort out the mess the Nationalists have made of the railways."

Mr Yousaf later announced a £19m upgrade to trains running between Edinburgh and Helensburgh and Milngavie, and admitted rail passengers "deserve better".

He said: "I understand passenger frustration. The standards that they expect are not being met and the standards that I expect ScotRail to meet are not being met either.”

The upgrade of the fleet of c334 trains will increase the number of six-car trains able to run on the network and improve reliability, Transport Scotland said.

READ MORE: Kenny MacAskill: Scottish Transport Minister Humza Yousaf not responsible for ScotRail debacle

Phil Verster, ScotRail Alliance managing director, said: "We are going through the biggest improvement in our railway since the Victorian era and this investment in our rolling stock is another significant signal of our determination to deliver a railway of which Scotland can be proud."

Responding to Ms Twyning’s comments, Mr Yousaf said the government was committed to a “successful” ScotRail Alliance in which both sides “should have a clear understanding of their respective roles and contributions in meeting passenger expectations”.