The government is considering giving any future Northern Ireland Assembly the power to raise a special police charge in addition to the regional rate.
The charge, known as a "policing precept", is levied throughout the rest of the UK as an element in council tax.
However, the chair of the Policing Board's finance committee, DUP MP Sammy Wilson, is concerned that the precept could be a "stealth tax" used to plug projected deficits in the PSNI budget of anything between £50m and £80m per year.
Currently, the annual PSNI budget is in the region of £720m, but the Treasury is regularly asked to pay a top-up within the financial year which can be between £30m and £40m.
Policing is an expensive and unpredictable business - the cost of policing last September's loyalist disorder associated with the Whiterock parade in west Belfast has been estimated as £3m.
Northern Ireland could be facing a "police tax"
Recently, the government wrote to the Policing Board warning members that in the medium term the purse strings on the police would be tight.
As part of a comprehensive spending review of all areas of government, two reviews are about to be launched which could have an impact on policing.
One is described as a "value for money" review of police and PSNI civilian staff numbers, another will deal with community safety partnerships and district policing partnerships.
The reviews are due to begin early next month and conclude by June.
'Stay within budget'
One particularly expensive project is the new police training college due to be built in Mid-Ulster.
Its capital cost is reckoned to be £130m. So far, the government has secured up to £90m for the project.
In the longer term, the government is looking to follow the example of police authorities elsewhere in the UK which are estimated to raise around 16% to 18% of their costs locally.
In Manchester, for example, people pay £110 per year towards the police.
In Liverpool, the figure is £115 and in South Wales it has just gone up to £126.
Manchester has just announced plans to axe 216 police officer jobs to stay within its budget and its chief constable has described his force's latest budget settlement as deeply disappointing.
Policing the disorder which followed the Whiterock parade cost £3m
Government sources say a future NI assembly could use the precept to enhance local policing, or could leave it at zero if they don't want to raise the regional rate.
But Sammy Wilson is concerned that the new charge will be used to meet basic policing costs.
He wonders whether the Treasury will remain ready to bail the PSNI out after any future civil disorder, and he questions whether central government will agree with local politicians on the numbers of officers needed to police Northern Ireland.
Currently the PSNI has 7,500 officers. A reduction to 4,500 would bring it into line with the rest of the UK.
But Mr Wilson says such a move is "not logical, advisable or desirable" given the unique security situation.
There are 820,000 ratepayers in Northern Ireland and the average rates bill is £550.
So the kind of police top-up common in England, Scotland and Wales would represent a significant increase in the overall bill.
While water charges and increased rates are due to be levied from April next year, it is not clear when, if ever, the new "cop tax" might bite.
That is because it is being linked to the devolution of policing and justice, which depends on agreement being reached between unionists and nationalists.
Some ratepayers might think that is a good financial reason for the politicians never to agree.
However, given the underlying economic realities if the "precept" is not introduced, there is no guarantee that direct rule ministers will not find some other way to make people in Northern Ireland contribute more towards their own policing.