SCOTLAND's embattled police chiefs have warned of a looming budget crisis.

Bruised by weeks of controversy over stop and search, the new national force looks set to plead the Scottish Government for millions of pounds more to complete its reforms.

Police Scotland fears it will not have enough money to invest in the new technologies it needs to deliver efficiencies after it loses a special reform budget at the end of the coming financial year.

The warning, made in official papers by its civilian oversight body, the Scottish Police Authority (SPA), comes after Chief Constable Sir Stephen House was this week grilled by MSPs over stop and search.

Sir Stephen had to admit his force - still undergoing a complicated and expensive IT overhaul - had lost vital data on how many stop and searches were being carried out.

The SPA's formal register of corporate risks, published this weekend, spells out new financial threats facing the force.

Police Scotland is currently receiving an extra £70 million a year on top of its normal budget to cushion the costs of the merger, including redundancy payments and desperately needed new IT.

However, the additional funding ends a year from now. The SPA - which measured the risk at maximum level for both likelihood and impact - said: "The Police Reform Budget has been extremely valuable in facilitating the first phase of building a national police force.

"Currently there is a risk that further development and the ability to realise efficiencies from more fundamental change will not be possible with the relative limited budget afforded to the SPA for this activity."

Calum Steele, general secretary of the Scottish Police Federation, warned that the papers showed that policing in Scotland was facing challenging times.

He said: "This report serves to reinforce that in the face of shrinking budgets and the imminent end of the 'additional' reform funding that the success that is policing in Scotland is under threat.

"This should serve as a wake-up call for government and the SPA that simply cutting budgets risks undermining the entire reform agenda as well as weakening the successful policing of our communities as a result."

Scotland has so far avoided dramatic cuts to policing seen in England and Wales and the single force was designed to make savings without hurting the front line.

However, SPA and force insiders have long warned that the police was facing potential financial problems.

In another "maximum risk" - renewed this weekend - the SPA warned projected budget savings for the 2015/16 financial year may not materialise, meaning it would either have to seek more money from the government or face a "drop in service".

The force is on track to save £68m this financial year.

Sources familiar with the process believe the force can balance its budget in 2014/15 but are deeply concerned that cuts will come in the next financial year.

The SPA's paperwork suggests that both the SPA and the force will now lobby the Scottish Government to continue reform funding.

A spokesman for Scottish Labour said: "Police officers and the Scottish people deserve to know who is responsible for this apparent shortfall and why it has happened."

Sir Stephen House will address a full meeting of the SPA on Tuesday - his second this month. However, a draft budget for 2015/16 will not be discussed until the authority meets next month.

An SPA spokesman said the force was working with the authority on its budget proposals.

He added: "Risk registers exist to assist organisations in identifying potential risks and the work required to mitigate them. The references to future financial challenges reflect that this remains ongoing work to firm up future spending and investment plans.

"The finance update being presented to the same SPA board meeting next week shows that Scottish policing remains on track to balance its budget this year, and there remains every confidence that policing will meet the target of delivering £1.1 billion of savings by 2026."

A spokesman for the Scottish Government said it would continue to make funding available to the Scottish Police Authority/Police Scotland to "support activities across a range of areas to enable them to generate the savings that are required".

He added: "Spending for 2016 -17 onwards will be the subject of the next spending review. The SPA has identified potential issues, however a range of activity is in place to ensure they are managed.

"The single service is safeguarding policing from Westminster budget cuts, protecting and improving local services by reducing duplication and enhancing access to specialist equipment and expertise.

"The benefits of reform are being realised in many ways, including the rationalisation and management of the police estate; reductions in administration, transport and supply expenditure in relation to procurement; the management of police officer numbers; and improvements in ICT."