A trading standards officer told a court how he received hundreds of complaints about an alleged scam website.
Andrew Stephenson from Sunderland Council's Trading Standards department said he counted 592 complaints with a value of £269,000 about the taxreturngateway website.
The four men who ran the site, Richard Hough, Michael Hughes, Jamie Wyatt, and Stephen Oliver, are alleged to have made more than £5million in five months from it.
Hundreds of users complained they were misled into believing they were dealing directly with Her Majesty's Revenue and Customs (HMRC), Teesside Crown Court heard.
Users thought fees of between £150 and £1,000 paid to the site would come off their tax bill, but the money was kept by the site as fees.
Mr Stephenson said he first became aware of the four men's business activities when he received 'inquiries' from customers about another website the men were running from offices in the Arrow Business Centre in Foyle Street, Sunderland, then later from offices in North Hylton House in North Hylton Road.
"As part of my inquiry I asked to be given a list of all their websites," Mr Stephenson told the jury.
"That was the first time I became aware of taxreturngateway.
"We then started to get complaints about that site from customers, and via referrals from other trading standards departments elsewhere in the country.
"I am aware there was some press publicity about taxreturngateway, and the complaints snowballed.
"We received more than 100 in a little over a week."
Mr Stephenson said that as part of his inquiry he logged on to the site.
"I had some concerns," he added. "The layout of the site seemed to have been created to look like a government agency site, and could have been confused as one.
"I was also concerned about the pricing, which was hidden away.
"You didn't see until the end of the process how much you were being asked to pay."
The court was told of a series of meetings and emails between trading standards and the four men.
"At one meeting they appeared agitated and annoyed," said Mr Stephenson.
"They seemed to think they had been unfairly targeted by the Press, and were seeking some kind of official approval from us for the website.
"They were keen for us to take their side, they wanted confirmation from us the site was legitimate.
"Given the growing number of complaints, and given what I had seen of the site, I couldn't justify that kind of approval."
In an email to trading standards from Stephen Oliver, taxreturngateway said it was a 'check and send' website, had satisfactorily dealt with 13,490 customers, and had 1,901 customer transactions classed as 'errors and omissions'.
"I call those errors and omissions complaints," said Mr Stephenson.
"I received another email from Mr Oliver in which he said his legitimate local business employing 25 people which had paid £750,000 in tax and VAT in the last quarter could be forced under by a campaign from a journalist.
"He said journalists had been knocking on the doors of neighbours of the directors, and there had been threats of violence.
"He said allegations the website was misleading were all myths, and he couldn't refund dissatisfied customers because the Press would portray that as a victory.
"I thought the email was a bit of a rant, but what concerned me from a trading standards point of view was he seemed not to care what the consumers thought.
"I was in the process of compiling a report for our national e-crime team, so we took the decision at that stage we could no longer advise taxreturngateway."
The court heard some refunds were made to customers, but that process was hampered because taxreturngateway's card payment facility had been withdrawn due to the number of complaints about the website received by the payment service provider.
Wyatt, 27, and Hughes, 26, both of Peartree Rise, Seaton, Seaham, Oliver, 47, of The Folly, West Boldon, and Hough, 43, of Thorpe Waterville, Kettering, Northants, each deny conspiracy to defraud between June, 2013, and June, 2014.
Wyatt, Hughes, and Oliver deny a second charge of conspiring to defraud by denying consumers the right to cancel under distance selling regulations.
The trial is in its second week, and is expected to take eight weeks.