The Met police has been told it needs to improve after an overall assessment of its ability to keep the public safe and reduce crime.

The report comes a week after Cressida Dick was appointed as the new Commissioner of Scotland Yard.

"I’m looking forward immensely to protecting and serving the people of London," she said after being appointed.

The overall findings prompted an official watchdog to raise the alarm over the "potentially perilous" state of British policing.

HM Inspector Zoe Billingham stopped short of saying the service was in crisis, but warned: "We are leading to a very serious conclusion regarding the potentially perilous state of British policing."

"Over the last few years, HMIC has said consistently that police forces were managing well in increasingly difficult circumstances.

"Nonetheless, today, I'm raising a red flag to warn forces of the consequences of what is, to all intents and purposes, an unconscious form of rationing of police services."

Brian Paddick, Liberal Democrat home affairs spokesman and a former senior police officer, described the findings as "totally unacceptable", adding: "How long will it be before someone dies because there is no police officer to respond?"

HMIC said it was warning for the first time of a national crisis in the shortage of detectives and investigators in many forces.

This was leading to excessive workloads, while complex investigations were being led by those who lacked appropriate experience. In one instance, inspectors saw a uniformed officer investigating rape.

The report highlighted the extent to which forces were not taking inquiries further because the victim did not support police action.

In some areas, more than one in five cases were not investigated fully for this reason and the issue was particularly acute for domestic abuse.

The watchdog examined the effectiveness of forces in England and Wales, and said that most provided a largely good service in keeping people safe and preventing crime.

Overall, one force was judged to be "outstanding", 28 forces were "good", 13 "require improvement" and one was rated "inadequate".

Michael Barton, National Police Chiefs' Council lead for crime operations, noted that the inspection found that most forces were "good overall" but said it was "disappointing" that HMIC also had concerns that some were "falling short".

He cited budget reductions and the loss of thousands of officers and staff, adding: "It's a simple reality that we are required to prioritise more.

"Difficult decisions are being made between resourcing neighbourhood teams, response units, specialist investigations and digital and cyber enabled crime."