Chief Constable Stephen House of Strathclyde Police said a regional structure would involve all the costs of merger without the savings a single force would bring.
His comments are a direct challenge to the Scottish Government, which is considering whether to move to one, three or four forces, after a consultation that ended this month.
The Scottish Police Federation, which is against a single force, is also opposed to a regional structure.
The federation, which represents more than 17,000 rank and file officers, believes the case has not been made for a single force, but agrees with the Strathclyde chief constable that three or four forces is not an option.
Mr House said: "The best model would be a single force. Three forces would be a fudge, with all the expense of change and none of the benefits.
"I would prefer we stayed with eight forces, at least that way we wouldn't have the initial expense. However, a single force is the right model of policing for Scotland."
He added: "There have been some misleading views expressed. One is that a single force would mean the end of local policing.
"I would argue the complete opposite, that it would improve local policing. You would have to have a highly devolved model where the key people would be local commanders and their relationship with local agencies and councils."
The police federation voted overwhelmingly against a single force last month, warning there has been too little evidence supporting the assertion that it would be more cost effective than the current eight.
However, it is equally opposed to the regional model.
Les Gray, chairman of the federation, said: "We recently voted by a fair majority in opposition to a single force and we stick by that.
"But we agree with Mr House - if you're going to make it three or four, it won't be cost effective, and we should stick to the status quo.
"Our stance from day one has been to ask whether the country afford it? Will it provide a better service? If the answer is no then, quite clearly, we should not do it.
"We should not do it for the sake of doing it."
A Scottish Government spokesman said: "No decision has been taken on reform. A consultation on the future of Scotland's police service closed earlier this month and the responses will be published in due course.
"These responses, together with the developing evidence, will be taken into account."