Media playback is unsupported on your device Media caption Theresa May: "There has been a proper process"

Ministers are "not picking a fight" with police by appointing an outsider as Chief Inspector of Constabulary for England and Wales, Theresa May said.

The Police Federation has criticised the choice of lawyer Tom Winsor - the author of a controversial review on police pay - for the important role.

The home secretary said Mr Winsor had "not been plucked out of thin air" and had been chosen in a "proper process".

The constabulary should be independent of ministers and police, she added.

Mr Winsor, formerly the rail regulator, will appear before the Commons Home Affairs Select Committee before his appointment is finally approved.

'Shine a light'

The committee will meet when Parliament returns on Monday to decide on a day for the hearing.

While the committee does not have the power to veto the appointment, its chairman - Labour MP Keith Vaz - has written to the home secretary to express his concerns about the timing of the announcement and to say more time is needed to consider the matter.

HM Inspectorate of Constabulary Image caption Tom Winsor was the author of last year's report into police pay and conditions Responsibility for police forces and organisations in England, Wales and Northern Ireland

Carries out inspections and publishes reviews and recommendations

Also inspects and regulates bodies such as the Serious Organised Crime Agency and HM Revenue and Custom Source: HMIC

Mr Winsor, 54, would be the first person who has not served as a police officer to take up the role since Her Majesty's Inspectorate of Constabulary (HMIC) was first established in 1856, opponents claim. He would replace Sir Denis O'Connor, who retires at the end of next month.

It is understood that in the final shortlist of candidates Mr Winsor was the only one with a non-police background.

Official procedure

The appointment has been questioned by the Police Federation, which represents rank-and-file officers and the Police Superintendents' Association of England and Wales, which said someone with "profound understanding" of policing was needed.

Mrs May would not be drawn on their comments and defended the appointment, which was made after she and policing minister Nick Herbert interviewed the main candidates.

"We are not picking a fight with anybody," she told the BBC's Andrew Marr show. "We did not just pluck Tom Winsor out of thin air. There has been a proper process under civil service rules."

She said HMIC had become more "independent" under Sir Denis O'Connor and its role would continue to change in future - including it reporting to Parliament rather than ministers.

"I think it is right that the body whose job it is to shine a light on policing and the police force should be independent of government and of the service," Mrs May added.

She acknowledged it was a difficult time for the police as there was "a lot going on at the moment" but she said ministers were determined to make it easier for them to do their job while increasing accountability through the election of the first crime commissioners later this year.

Controversial report

In his report into police pay and conditions last year , Mr Winsor called for the abolition of a series of allowances and special payments and for a pay system that recognised hard work and merit instead of long service.

He also recommended that officers on frontline duties should see their pay rise, and wanted a professional accreditation allowance of £1,200 to be introduced for most detectives, firearms, public order and neighbourhood policing teams.

The HMIC has increasingly been drawn into controversy as the political debate on cuts to police budgets has intensified.

In 2010, the HMIC suggested that a 12% funding cut was achievable, but going further risked damaging frontline policing in England and Wales.

Labour have accused the government of ignoring its advice and pushing ahead with 20% cuts over four years, saying it will result in thousands of fewer police officers.

But ministers insist changes to police practices and priorities will increase the number of hours officers spend fighting crime rather than on paperwork and administration.