Two other directors were found not guilty in December after judge threw out the case

The last of the three Tesco executives accused of masterminding a fraud that triggered a financial crisis at the company has been acquitted, leaving the Serious Fraud Office without a single conviction for the accounting scandal that wiped £1.5bn off the value of Tesco shares in one day.

Carl Rogberg, 52, who was cleared in Southwark crown court on Wednesday morning, claimed the four-year ordeal had contributed to a heart attack that forced the original trial to be abandoned last year. The legal case had taken an enormous toll on his health as well on the lives of his wife and young son, he said.

“How do you explain to your eight-year-old son what is going on?” Rogberg told the Guardian. “He’s now 13. His whole childhood has been, I wouldn’t say wiped out, but significantly influenced by what has been going on.”

“I’m back to full health,” added Rogberg. “That is the really good part.”

Two other former Tesco directors, Chris Bush and John Scouler, were acquitted in December after the judge Sir John Royce threw out the case. Royce said the prosecution case was “so weak” it should not be before a jury. Rogberg was not part of that retrial because he was recovering from a quadruple heart bypass.

Despite Royce’s withering assessment of the SFO case, the agency maintained that it was still considering pursuing a retrial of Rogberg. However on Wednesday it offered no evidence and Judge Deborah Taylor formally entered a verdict of not guilty.

Sasha Wass QC, representing the Serious Fraud Office (SFO), said: “The SFO has considered the matter carefully and, given the acquittals of the other two defendants, [decided] it would not be fair to try Rogberg on his own and for that reason we offer no evidence against him.”

The collapse of the case raises questions about both the calibre of the SFO’s investigation and Tesco’s decision to strike a £129m plea bargain, known as a deferred prosecution agreement (DPA), in 2017. The US-style transaction involves a deal brokered between the prosecutor and an accused business to avoid a full trial.

The case stemmed from one of the most shocking episodes in recent corporate history, discovered weeks after Dave Lewis took over as chief executive, replacing Philip Clarke, who had had been axed after a big decline in Tesco’s fortunes.

On 22 September 2014, Lewis told the City that forensic accountants and lawyers had been called in to scrutinise its books after a whistleblower claimed payments from suppliers were being manipulated to make the supermarket group’s finances look healthier. At the time, Tesco said the rogue practice had inflated profits by £250m.

The following day the three executives were suspended from their roles and never returned to work for the company.

In the DPA, which has now been made public, Tesco accepts false accounting took place at its Tesco Stores Limited subsidiary between February and September 2014. It named the three executives and said they “dishonestly perpetuated” a profit misstatement and were involved in “falsifying or concurring in the falsification of accounts”.

The SFO defended its investigation, stating that in the six-month period it discovered a culture existed at Tesco that encouraged “illegal practices to meet accounting targets”. Lisa Osofsky, the crime agency’s director, said: “The DPA clearly outlines the extent of this criminal conduct for which the company has accepted full responsibility.”

But Rogberg said there were “serious questions” for Tesco and the SFO to answer: “All three of us have been acquitted. It’s not just an acquittal it’s a super-acquittal. There’s no guilt what so ever and the case has been stopped by a number of judges. Yet on the same day a DPA has been published with us named in it.”

Ross Dixon, a partner at the solicitors Hickman & Rose, who represented Bush throughout his trial, called for the “urgent reform” of the DPA process. He said: “We now have two contradictory outcomes: that of the criminal trial in which the allegations were dismissed for lack of evidence and the DPA based on the same allegations.”

Tesco, which handed over 1,600 bags of documents for the SFO to inspect, said it had signed the agreement after the profits overstatement was “independently investigated and verified by [the accountancy firm] Deloitte”.

In a statement the supermarket said it was now “a very different company”, adding: “This DPA was also separately approved by a senior high court judge, LJ Leveson, as being in the interests of justice.”