The official website for communicating public data in the UK is "terrible" and a "disaster", MPs have told the man responsible for the service.
Andrew Dilnot, the chairman of the UK Statistics Authority, conceded that a relaunch of the Office for National Statistics (ONS) website last year had not been "one of our greatest moments".
But he emphasised that there had been "significant" improvements recently.
A Tory MP said he had been shocked by how poor the website had become.
The UK Statistics Authority oversees the ONS, and Mr Dilnot said its board, which he chairs, was ultimately responsible for the website.
The chairman of the Commons Public Administration Committee, Bernard Jenkin, told Mr Dilnot he had heard "excoriating" evidence on the website's quality.
On Tuesday, fact-checker Will Moy of fullfact.org had told the committee that navigating official statistics websites could be like venturing onto a "magic roundabout".
"You can get lost very quickly at the ONS website," he warned the assembled MPs.
"Our official statistics producers are sitting on a treasure chest of data which can inform and illuminate our public debate, and sometimes they are literally sitting on top of them, daring you to get in.
"What they should be doing is presenting it, and saying: 'We have all this information, and it can help you; it can help you as citizens, it can help you as businesses... and this is how it can help you.'"
Michael Blastland, a freelance journalist who used to work on More or Less, the BBC Radio 4 programme examining statistical claims in political debate, had a confession for the committee.
"Just before I left [the programme] I had an idea that I'd get myself a couple of very bright maths graduates and shut them in a room and say, 'see if you can find a long-run series of data since the second world war of per-capita GDP'," he said.
"Quite an interesting little number. And you pop in every couple of days with bread and water just to check they weren't dead."
He concluded: "It is an exasperating experience."
Chris Giles, a senior journalist at the Financial Times, posed a seemingly straightforward question: "Is unemployment now higher or lower than it was in the mid-1990s?"
Having spent some time analysing the ONS website, he declared: "There is absolutely no way of getting an answer to that question if you are a lay person."
Even for expert users, like himself, "it takes eight clicks... that is really very, very frustrating."
The committee also grilled the minister at the Cabinet Office responsible for policy on publishing statistics, Conservative MP Nick Hurd.
Labour backbencher Paul Flynn described his performance as "sad" and "disappointing", saying the minister displayed little mastery of his brief.
"You have observed, Mr Hurd, that since you started your evidence to this committee, several Conservative members have left; whether it's embarrassment, or guilt, or..." he said, before he was interrupted by the committee chairman.
Mr Flynn added: "The changeover to the new [ONS] website was generously described as a disaster. In fact it was probably worse than that. The journey that you're taking is one backwards, into a denial of information."
Mr Hurd rejected Mr Flynn's claims, adding: "Please don't underestimate what is going on in terms of the open-data agenda, which is being driven by the Cabinet Office."
There was "widespread engagement with people who look at statistics, look at data; widespread engagement with people who want to make businesses out of that".
The comments from the committee's session on Tuesday were put to Mr Dilnot when he appeared before it on Wednesday.
He revealed a degree of nostalgia for the former ONS website, which he said he had bookmarked in his browser long before being appointed to the top job at the UK Statistics Authority.
"Four of five years ago, I thought it did what then seemed to be a good job. I've said repeatedly that we have in this country marvellous data, an extraordinarily rich array of professionally produced statistics," he told MPs.
"The relaunch of the ONS website in August of last year was not one of our greatest moments, and at that time the website became difficult to use, difficult to navigate, difficult to search."
He said the ONS web team had made "significant progress" towards resolving the problems, particularly by improving the search function in the past fortnight.
But Conservative MP Charlie Elphicke seized upon the admission, declaring that the problems with the website had been "endlessly frustrating" and "shocking to all of us who are anoraks".
"Would you accept it's been pretty terrible, it needs a lot of improvement, and you're on the case? And the search is just awful, and that needs improvement?" he asked.
"Are you going to say to us, we get it and we're on the case?"
"Absolutely," replied Mr Dilnot, pointing to the progress being made, adding that before appearing before the MPs he had tried to defeat the new search function, but without success.