THE behind-the-scenes power struggle that risks overshadowing next month's merger of Scotland's eight police forces has been laid bare in explosive correspondence obtained by MSPs.

The file shows Justice Secretary Kenny MacAskill was forced to overrule the Scottish Police Authority (SPA), the watchdog overseeing the new national force, when it tried to commandeer civilian police staff, a move the Government branded "unbalanced and confusing".

The merger of the eight forces on April 1 is designed to make policing in Scotland more efficient and save £1.7 billion over 15 years. However, the process has been plagued by rows between Chief Constable Stephen House and SPA boss Vic Emery.

In January, with the turf war raging, the SPA tried to wrest control of police finance and HR staff under "organisational principles", and tabled an SPA board paper to make it official.

However, just before the SPA board could act, MacAskill stepped in to squash the idea.

The SPA has until now downplayed MacAskill's direction, but Holyrood's justice committee refused to accept "selected quotes" and Emery has now surrendered the full correspondence, which the committee will discuss on Tuesday.

On January 17, the day before the key SPA board meeting, one of MacAskill's officials, director of safer communities Paul Johnson, wrote to Emery.

Johnson made it clear MacAskill backed House's position that the police should be in the lead. He wrote: "The Scottish Government is of the view that the proposed arrangement is unbalanced, confusing and would place the Police Service of Scotland in a unique and invidious position."

"The Cabinet Secretary has requested that the SPA board adjusts the Organisational Principles to ensure that the Chief Constable has access to police staff to assist him in relation to his administration responsibilities."

Emery grudgingly agreed to the compromise, but complained the changes were "neither modest nor insignificant". He added: "I further stress that it is with more than a little reluctance that the board has agreed to this request at this 11th hour.

"There will be many further issues before police reform is fully delivered which will require difficult decisions, and the board's reservoir of patience with the protracted nature of resolving this kind of issue is already running low."

Labour MSP Graeme Pearson, a former head of the Scottish Crime and Drug Enforcement Agency, said the justice committee had to "wheedle" the papers out of the SPA, and that the divisions they revealed were still a significant problem.

"This fudge ... could become a war of attrition, with the two sides undermining each other's position through petty bureaucracy," he said. "It is the moment to say, 'Enough is enough'."