The claim: Life expectancy in Britain has fallen by six months in the first drop since 1945.

Reality Check verdict: Life expectancy in Britain has not fallen by six months, according to the report cited by Labour. But improvements in life expectancy have stalled.

Jeremy Corbyn and Theresa May had a disagreement about life expectancy during Wednesday's Prime Minister's Questions.

Mr Corbyn said that life expectancy in Britain had fallen by six months, the first time there had been a fall since 1945.

Mrs May responded: "It is not the case that people are now expecting to live shorter lives."

It is generally agreed that growth in life expectancy has slowed in recent years - and it has fallen for some social groups and in some areas.

The Office for National Statistics (ONS) says that overall in the UK life expectancy at birth has stalled - meaning there was no increase between 2015 and 2017 - the first time that has happened since these particular calculations started in 1980.

There was also no improvement in life expectancy at the age of 65, which is a key metric for pensions providers.

So, on that basis, the prime minister is right to say that people are not expecting to live shorter lives - but it is also the first time in at least 40 years that they have not been expecting to live longer lives.

BBC Reality Check asked Labour for the source of Mr Corbyn's claim and was told that it came from this Public Health England report. But the report does not refer to a six-month fall in life expectancy - it is based on the ONS figures, which suggest life expectancies have stalled but not fallen overall.

But there is another source that looks as if it may be suggesting a six-month fall in life expectancy.

Many institutions such as insurance companies use figures from the Continuous Mortality Investigation produced by the Institute and Faculty of Actuaries.

The latest version of that came out in March. It found that life expectancies at the age of 65 had been about six months shorter for both men and women in 2018 than they had been in its report in 2017.

That appears to support Mr Corbyn's claim that life expectancy had fallen by six months, but the people who produced the report stressed that much of the six-month fall had been due to a change in the way they worked it out, including giving more weight to what has been happening to life expectancy since 2011.

It means the 2017 and 2018 figures are not strictly comparable.

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