The proposed merger of British Transport Police (BTP) with Police Scotland has been delayed.

It comes after the joint programme board appointed to oversee the integration of the two forces said a "longer timetable" was needed.

This, the board said, would allow more time for engagement with officers, staff and their representatives on key issues, including pay and conditions.

A "re-planning" exercise will now take place over the coming months before a fresh date is set for the merger.

Justice secretary Michael Matheson said: "While much has been achieved so far, we want to ensure a seamless transition which delivers continuity of service for rail users and staff.

"While a later integration date is disappointing, it will provide all partners with the opportunity to enhance the process of engagement, in particular with officers, staff and their representatives on key issues."

Mr Matheson went on to confirm the Scottish Government's commitment to its "triple lock" guarantee to protect the jobs, pay and pensions of BTP officers transferring to Police Scotland.

The proposals, which were passed in a narrow vote at Holyrood last June, continue to draw criticism from unions, opposition parties and the BTP Federation, which represents transport police.

Scottish Liberal Democrat justice spokesperson Liam McArthur MSP said: "Inexcusably, SNP ministers failed to do the basic work to identify and plan for the risks and implications of their latest centralisation.

"Instead, they landed the joint board with the task of implementing this policy at any cost. It didn't take long for those left to conduct the merger to deliver their verdict.

"With so many questions left unanswered, it was always risky and unrealistic to proceed with the SNP's timetable for disbanding the British Transport Police in Scotland. It now seems that the joint board agrees."

A statement from BTP said: "We remain committed to ensuring any proposed merger goes ahead as smoothly as possible, both for our own staff and for rail passengers in Scotland."