Earlier this month, FactCheck called the government out on the claim that it is spending more than ever on flood defences.

Vulnerable to accusations that cuts had left swathes of the country exposed to freak storms, ministers tried to play down the extent to which coastal defence budgets have been slashed under the coalition.

The problem was that the hard evidence was there for all to see in the latest figures from the Department for Environment, Food and Rural Affairs (Defra).

The coalition had taken the decision to cut annual spending by almost £100m in a single year, and more than £200m over four years in real terms.

We highlighted the string of ruses that were employed to get around this fact.

Ministers started talking about “the first four years of this parliament”, including 2010/11, when Labour’s spending plans were still largely in place.

In other words, they were trying to take credit for the high levels of spending they inherited from the previous government, despite having decided to cut back on that spending themselves.

They also tried to count money pledged – but not yet delivered – by councils and businesses as “government spending”.

And the government insisted on talking about the money in cash terms. The claim only stood up if you forgot about inflation.

We came up with our own unofficial inflation-adjusted figures, and we thought that, even with David Cameron’s sudden decision to pump an extra £130m into the flood defence budget over two years, there were big holes in the government’s position.

We thought spending was still less over the four years starting from 2011/12 (the current spending period) than over the previous four years.

Now the chair of the UK Statistics Authority, Sir Andrew Dilnot, has added his authoritative voice to the growing doubt over the government’s use of statistics.

In answer to a letter from Labour MP Hugh Bayley, Sir Andrew writes: “As at January 2014, government funding for flood defences was expected to be lower in both nominal and real terms during the current spending period than during the last spending period.

“Our analysis also supports the conclusion that the statement ‘over the current spending review period, more is being spent [on flood defences] than ever before’ is supported by the statistics if the comparison is made in nominal terms and includes external funding, but it is not supported by the statistics if the comparison is made in real terms, or if external funding is excluded.”

Sir Andrew also says Defra has not explained why it suddenly revised its estimates on flood defences upwards, and notes that these spending figures are not official statistics, so there is no obligation for the department to comply with the official code of practice.

He suggests that: “It would better serve the public good if Defra were to consider publishing official statistics on expenditure by the relevant organisations on aspects of flooding and coastal erosion management in future.”