Simon Read: You're guilty until proven innocent when HMRC sends in the tax credit detectives

When Mary Folwell got a letter from HM Revenue & Customs last month, she put it to one side assuming it was just a standard reminder that her tax credits would be renewed.

When she got round to opening it, she had a shock. It was actually from an HMRC-appointed agency named Concentrix – and it accused her of living with someone and threatened that unless she could prove otherwise, her tax credits would be stopped within 30 days.

"It said they had evidence to suggest that I was living with someone, which sent me off into panic mode," Mary, a 55-year- old pre-school teacher in Bristol, told me. "I separated from my husband two years earlier and had moved into a small flat on my own. There really has never been anyone else here."

The letter threatened that if Concentrix did not hear from her by 24 February, "we will stop your tax credit". "I only get £15 a week," explained Mary – "which may not seem much but it's crucial to my budget. If I lost that money, I would really struggle."

She's not alone. Tens of thousands of people – mainly single mothers, it seems – have been targeted with similarly bullying letters. The letters are not only frightening, but their demands are needlessly onerous. In short they demand that people supply almost all their personal details to prove some spurious suspicions that HMRC may have. Failure to do so within a couple of weeks means losing out on essential cash for which they are eligible.

"I rang them up to explain that nothing has changed from when I applied for tax credits, but they just told me I had to send all my bank statements from April to this January – as well as my rental agreement, gas bills and other information – to prove that their accusations were not true.

"And they wanted all original documents, which was quite a problem and distressing, especially as I had to get a letter from my solicitor as well to confirm my divorce," Mary said.

She managed to get it all together this week and send it off by the Wednesday deadline, but is now biting her nails and hoping it arrived in time and all is well.

But judging by the way in which this company has gone about its business so far – with the full authority of HMRC – it would be no surprise to discover that Mary, and hundreds of thousands of others, have had their tax credit arbitrarily cut in the latest example of needless bully-boy tactics by the Government.

If you visit the online forums on Mumsnet or Moneysavingexpert, you'll find plenty more tales of distress and worry. I was contacted this week by one Twitter user, who simply said: "I feel suicidal because of it." Ominously, she hasn't posted since.

I spoke to Concentrix. It simply said: "We are committed to delivering a professional and efficient service to our customers." It appears to be doing that by filling people with needless fear and distress. The wild accusations are alarming and unnecessary. Of course HMRC has a right to check the credentials of those receiving tax credits – but not by employing such unpleasant methods.

All the victims to whom I've spoken have expressed utter surprise at the claims and threats in the letters. If HMRC really has concerns or vague "evidence" then it has no need to be so confrontational with what are likely to be vulnerable people.

HMRC told me: "We know how important tax credit money is and that it can be worrying for claimants when we carry out these checks. We don't want to worry customers unnecessarily; we're just trying to ensure that they don't end up being overpaid tax credits, resulting in a debt which then has to be repaid later."

But threatening to withdraw them is not a civilised way of going about things. When HMRC sorts out this mess, I expect it to apologise to every single person who received one of these threatening letters. That's the least it can do after causing so much anguish.

s.read@independent.co.uk

twitter: @simonnread