The former boss of Greggs, who built the bakery business into one of the UK's most successful high street chains, has become the first senior executive to break ranks with his peers and attack the level of boardroom pay in corporate Britain.

Sir Mike Darrington, who led Greggs for 25 years before his retirement in 2008, said: "The quantum of executive pay is excessive and must be reduced … if the current packages were halved, senior executives and bankers would still be overpaid."

Darrington, who was knighted in 2004 for services to business, has pledged to use his retirement to campaign against excessive boardroom pay deals. He hopes to encourage other like-minded business leaders to offer a critical perspective from inside the executive world.

In particular Darrington, 69, is keen to scotch the myth that attacks on executive rewards are attacks on business. "It is a smokescreen and a lot of bollocks – it is the greed of the people [at the top] that is anti-business." He has labelled his campaign "pro-business and anti-greed". He admits he had been sceptical about trends in corporate governance but claims remuneration has become such a toxic issue it must now be dealt with radically.

His condemnation of existing arrangements is the most searing criticism from the business establishment since Richard Lambert, then director-general of the Confederation of British Industry, two years ago warned bosses risked being viewed as "aliens [living in] a different galaxy from the rest of the community" because of the ever widening gulf between shopfloor and boardroom wages.

Darrington, who was born in Sussex but has lived much of his life in Jesmond, Newcastle, is seeking to build a broad base of support for a campaign to reign in executive pay. He is already supported by the High Pay Centre and corporate governance advisory group Pirc, but is keen to get public backing from fund managers and, ultimately, executives themselves.

In 2007, as Greggs chief executive, Darrington received pay, benefits and bonus of £901,000 and, a year later, retired having built up a pension pot of more than £2m. His pay was modest compared with peers. Since the group joined the stock market in 1984 it has grown steadily, becoming a FTSE 250 stock, and proving one of the few high street success stories during the recession. It continues to open stores, creating jobs, while many of its peers rapidly contract or go to the wall.

Unlike many politicians who have joined the debate on executive pay recently, Darrington is also happy to cite specific examples of what he sees as unacceptable excess. He attacked the decision this month by Barclays chief executive Bob Diamond to trim back investment banker pay by a third. "If profits are down [nearly] 40%, bonuses should be nil," he said yesterday at a governance conference organised by Pirc.

Also criticised were past pay arrangements for former Marks & Spencer boss Sir Stuart Rose and former Tesco chief executive Sir Terry Leahy. Darrington suggested that during Leahy's final years Tesco's share performance had been "good but not brilliant — and look what happened since". Some £5bn was wiped off the value of the group last month after Leahy's successor Philip Clarke delivered a heavy profits warning and attacked the company's "long-standing business issues".

Darrington also dismissed fears that companies taking a hard line on executive pay risked losing vital business leaders to rivals. It would be healthy to cut back pay to such a level that executives left, he said, as most companies had a rich pool of talent which could step up to fill any roles left vacant. "If you don't start to lose people, we have not gone far enough," he claimed, though he accepted a mass exodus might indicate inappropriately low levels of pay.

The increasing complexity of pay arrangements is another bugbear for Darrington. He said multiple bonus arrangements, purporting to be linked to performance, were "guilty of obfuscation".

Reflecting on the many cases of executives received big payouts despite manifestly poor performance, he said the complexity of remuneration arrangements meant shareholders "do not know what is going on until it is too late".