STS Bulletin no.30
"I'm not sure I see a need to apologise."

means

"I am deeply sorry that people are facing an unexpected tax bill.
Everyone in HMRC is working hard to make this as painless as possible. I apologise if my remarks came across as insensitive. I am working flat out with my colleagues to ensure everyone's tax is correct and the new computer system will help us do this.
"It was this new system that revealed the extent and size of reconciliations required and will help us be more accurate in future but we do not underestimate the distress caused to taxpayers and once again I apologise."

It can also be translated as "Christ! I could lose my job over this. Better do a bit of grovelling."

The millions of people about to be harried and harassed by the penitent Mr. Dave Hartnett's underlings should appeal over their heads to the top man. It turns out he can be persuaded to write off tax arrears given the right circumstances, according to the current edition of 'Private Eye'.
Her Majesty's Revenue enforcers have been in hot pursuit of a little company named Vodafone for a paltry £6 billion. They had the case all tied up, all loopholes blocked, when the company appealed to Mr. Hartnett's better nature.
Quick as a flash Mr. Hartnett cancelled the debt. The revenue's legal team were appalled. They had Vodafone by the goolies and were about to squeeze hard. "No dice," said our Dave, "Concentrate on the little people. I might need a job at Vodafone if those MPs manage to get me sacked for incompetence."