Stunned Michael Williams was accused of fathering a child by the CSA - 15 years after having a vasectomy.

Mr Williams, 58, got the shock of his life when he received a letter from the Child Support Agency naming him as the father of a boy by a woman he says he has never met - or even heard of.

"I was shattered by it," said Mr Williams. "I've got a heart problem and this could have killed me off, I was so distressed by it. I was near to tears.

"I've never heard of this woman who is on the letter. And, apart from that, I had a vasectomy about 15 years ago."

The CSA has now admitted its mistake.

Mr Williams, who has four children from previous marriages and a stepdaughter and stepson with his current wife, said: "It's created havoc in my household.

"If it wasn't for the fact that she trusts me implicitly this could have ruined my marriage."

When he received the letter he took it to a solicitor, who spoke to the CSA, which said there had been a mistake and a letter of apology would follow.

But all he got was a letter from the Department of Work and Pensions, saying £5 week would be taken from his benefits indefinitely, even though he had not admitted to being the father of the child or undergone a DNA test to determine the answer.

"You hear of men committing suicide because of the CSA and less than this."

Mr Williams, from Washington, Tyne and Wear, added. "It's just not on."

The Government agency, responsible for assessing, collecting and enforcing child maintenance payments, acknowledged it had made a mistake.

A spokesman said: "The agency will be contacting Mr Williams to explain this error and we apologise for any distress this may have caused him.

"The CSA deals with more than one million cases and sometimes a mistake may be made."

A Government report released last month criticised the agency for false information being entered onto computer systems to speed up claims, and MPs have said it should be replaced unless it improves performance.