Top police officers engaged in a "power struggle" over major functions of the new national force have been accused of empire building.
Politicians issued an ultimatum to Chief Constable Stephen House, of the Police Service of Scotland, and Vic Emery, the chairman of its scrutiny body the Scottish Police Authority.
Both men sought legal advice over who controls police support staff under the terms of legislation which will merge the existing eight regional forces by April.
Holyrood's Justice Committee said there must be a resolution by January 18. MSPs on the committee also urged police to follow the example of the fire service, which they said appears to have had no problem dealing with the same transition to a single force.
John Finnie, an independent MSP, said: "Two empires have been built and it may be that trains are running that should be stopped at this early stage."
Labour MSP Graeme Pearson said trade unions are not being kept up to date with progress and said there seems to be a clash of personalities.
"It's being conducted at public expense and with some degree of public concern," he said.
Mr Pearson, a former policeman, said a "shadow group" appears to be emerging in the police authority which will replicate functions elsewhere.
"This was supposed to be about reducing management costs in order to protect front-end services," he said. "This doesn't reflect best practice and it seems to me the board has enough to do to bring a police service to account and to show good governance."
Last month, Justice Secretary Kenny MacAskill told MSPs that the two figures had almost resolved the issue, describing them as being "95% there".