MINISTERS have signalled a further push for full control of Scotland's railways, claiming "an honest conversation" was needed with the trains' operator over the causes for delays and disruption.

Transport minister Humza Yousaf said he planned to discuss the limited powers of the recently created Scotrail Alliance and the reasons for much passenger unhappiness when the firm's new chief takes the reins in June.

In a briefing to MSPs, Mr Yousaf described the operation, which has welded together franchise operator ScotRail with infrastructure manager Network Rail, as "optically flawed" and "work in progress", expressing ongoing frustrations over the impact of signal and track failings on customer delays.

The comments come as the SNP at both Holyrood and Westminster seek support for the full devolution of Network Rail, with all signalling and timetabling operated from Milton Keynes.

Champions of the move include former UK transport minister Tom Harris, with the Scottish Government claiming it would save the taxpayer £100 million a year and enhance customer experience on the railways by reducing journey times and delays.

One senior transport source told The Herald the recent improvement in Scotland's performance was largely due to "the Milton Keynes operation being told to get the finger out".

Others have claimed the nature of the relationship has meant ScotRail has taken the blame for issues beyond its control and been unable to rectify that.

Network Rail has said that the ScotRail Alliance “already provides a dedicated and devolved rail network to Scotland”.

The latest move comes Mr Yousaf announced that the delayed redevelopment of one of Scotland's busiest stations was ion the cusp on being unlocked.

Following claims by Network Rail that contractual and legal wranglings stalling the overhaul of Glasgow's Queen Street station, Mr Yousaf said the required Government authorisations, knows as TAWS orders, would be signed off within 48 hours following an eight months hold up.

Addressing Holyrood's Rural Economy and Connectivity (REC) Committee, Mr Yousaf said the former ScotRail Alliance chief Phil Verster had already left his post, with his replacement not due to be in place until June.

He said Alex Hines could not secure his release from train firm Arriva Northern until that stage. Asked whether the fact he would be ultimately employed by Network Rail present a conflict of interests, Mr Yousaf said: "I wouldn't say conflict of interest but ScotRail Alliance can seem optically flawed.

"I get very frustrated by delays caused by signalling or track flaws. When this is discussed with the person in charge of the Alliance the response was 'I don't have full control'.

"The Alliance is work in progress. We need to have an honest conversation about the powers that person has when appointed to head up the Alliance."

Meanwhile, Mr Yousaf said he did not anticipate the delays to Queen Street Station to impact upon train services but would be felt by the actual building. The minister said the electrification of the Glasgow to Edinburgh line would be completed and operational by July, that "greener, faster, longer" trains would run from the autumn, while an entire new fleet would be in place by December.