The claim: 1.7 million pensioners are living in poverty and a million in fuel poverty.

Reality Check verdict: The figure for pensioners who are defined as living in poverty in the UK is a bit higher than that at 1.9 million. There isn't a specific figure for the number of pensioners in fuel poverty in the UK but a million is not an unreasonable estimate based on the figures that we do have.

Shadow chancellor John McDonnell spoke to BBC Radio 4's Today Programme on Friday about the Conservative manifesto pledge to means-test winter fuel payments.

The Conservatives have not given any details of how they would apply a means test or how much they would hope to save.

The winter fuel payment is between £100 and £300 (depending on your circumstances) paid to anyone receiving a state pension or people of pension age receiving certain other social security benefits.

In winter 2015-16 it was paid to 12.2 million people, 42,000 of whom lived elsewhere in Europe.

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Mr McDonnell pointed out that since we don't know where the means test will fall, a number of less well-off pensioners could still lose the benefit.

He suggested it might just be people entitled to pension credit who would get the fuel allowance, although government sources have told the BBC that would not be the mechanism, and that there would be a consultation process to decide how it would be tested.

Pensioners with an income below £159.35 a week may claim pension credit - it's £243.45 for couples.

According to the latest figures from November there were 1.9 million people claiming pension credit, or 2.2 million if you include their partners, although there has been research suggesting that about one-third of people entitled to it are not claiming.

Mr McDonnell told the BBC that there were 1.7 million pensioners living in poverty and a million living in fuel poverty.

People count as living in relative poverty if they are in households with an income below 60% of the median household income. The median income is the one for which half of households have higher incomes and half have lower.

The government's preferred measure of pensioner poverty is after housing costs have been taken into account. Nearly three-quarters of pensioners live in homes that are owned outright (compared with roughly one in five of the working-age population) and so are less likely to have high housing costs.

On that measure, 16% of UK pensioners are in poverty, which is 1.9 million people.

There are also measures of absolute poverty, which may measure whether people are able to afford a basic lifestyle - about 8% of pensioners fall below the threshold for material deprivation.

To measure fuel poverty, the government looks at two things - how much you have to pay for fuel, and what your income is. You'll be considered to be in fuel poverty if your required fuel costs are above average and, were you to spend that amount, your remaining income would leave you below the official poverty line as explained above.

The latest government figures we have on fuel poverty relate to 2014 and suggest 2.38 million households in total in England were in fuel poverty.

There isn't a specific figure for the number of UK pensioners in fuel poverty, but according to Table 14 there were 621,000 households just in England in 2014 in which the oldest member was over 60. Age UK says this equates to more than 1 million individuals, although some of them will not yet be entitled to their state pension.

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