The claim: Police numbers have fallen by 20,000 since 2010.
Reality Check verdict: Labour's figures are about right. Latest statistics show that police officer numbers in England and Wales have fallen by 19,000 since 2010.
Shadow home secretary Diane Abbott said 20,000 police officers in England and Wales had been lost from the force since 2010.
Between September 2010 and September 2016, police numbers in England and Wales fell by 18,991, or 13%, according to the Home Office.
Police numbers rose gradually from the 1980s, with a sharp rise from around 2000. Since around 2010, however, they have been falling significantly.
The figures Ms Abbott points to are for England and Wales only, because policing in Scotland and Northern Ireland is devolved.
In Scotland, police numbers have risen more or less continuously since 1985, while in Northern Ireland there has been a decrease since 2010, but not as sharp as the decrease seen in England and Wales.
As of September 2016, there were 122,859 police officers working in England and Wales.
Up until 2010, spending on policing had been increasing for at least 15 years, rising most sharply between 2000 and 2010 when it went up by around 30%. But since then, spending has come back down significantly.
Although the Conservatives pledged to protect police budgets in real terms in 2015, this came off the back of five years of deep cuts amounting to 18% in real terms.
Numbers of Special Constables and Police Community Support Officers (PCSOs) who patrol the streets, have also fallen by 7% and 11% respectively in the last year alone.
No comprehensive research has been done into whether there is a link between falling police numbers and rising crime levels.
However, Her Majesty's Inspectorate of Constabulary (HMIC), the body which inspects police forces, has warned that cutbacks could put the public at risk.
Crime statistics are a tricky area in the first place, with numbers of crimes recorded by the police going up 9% in the last year, while levels of crime experienced by households when asked as part of a survey remained stable.
Police recorded crimes are not designated as national statistics because they are not considered reliable enough.
On this measure, crime fell between 2010 and 2014 and since then has been increasing, but a lot of this is down to changes in recording practices.
Knife crime in London has been rising for four years in a row and in 2016 the police recorded a 14% increase in offences involving a knife or sharp instrument compared with the previous year, across England and Wales. This is thought to be down to both a real increase in actual offences and to changes in recording practices.
Crimes, excluding fraud and cyber crimes, that were reported by households in a large scale survey - the Crime Survey for England and Wales - have fallen overall in this period.