The Apple antenna debacle has taken another twist with the surprise departure of the senior executive responsible for engineering the iPhone and the iPod.

Mark Papermaster, Apple's senior vice-president of devices hardware engineering, is leaving the company less than two years after he was controversially lured from IBM. The company would not say whether he had resigned or been dismissed, but his details have already been removed from Apple's corporate website.

Papermaster's exit sparked speculation he was paying the price for "Antennagate". It comes just six weeks after the launch of Apple's latest smartphone, the iPhone 4, which was marred by complaints that the handset's signal strength fell sharply when held a certain way.

Apple has now offered a free "bumper" case to all iPhone 4 users that fixes the antenna problem, and insists demand for the phone remains high. However, the episode has been labelled a rare PR blunder by the company, especially after chief executive Steve Jobs angered rival handset-makers by stating that the reception problem was common in the industry.

Papermaster had led the hardware engineering teams that designed Apple's iPhones and iPods. Although Apple would not say why Papermaster is leaving, spokesman Steve Dowlings confirmed that Bob Mansfield, senior vice-president of Macintosh hardware engineering, is "assuming his responsibilities".

There was no other official statement from Apple on the departure and the company did not respond to requests for comment.

Papermaster had only worked for Apple for just under 16 months. He had previously been employed for 25 years at IBM, where he was a leading expert on its Power chips. IBM launched a legal challenge when Apple appointed Papermaster in October 2008, claiming that he would divulge trade secrets. The two sides eventually agreed that Papermaster would wait six months before joining Apple, and promise not to reveal confidential IBM information to his new employer.

Apple has said it hired Papermaster because he had "strong general engineering skills, is an outstanding leader, and because we believe he will be a good cultural match at Apple". Papermaster called the move a "once in a lifetime" opportunity.

John Gruber, who blogs about Apple at Daring Fireball, said it was "clear he [Papermaster] was sacked", pointing to his absence from the 16 July press conference when Jobs discussed the antenna issue. One analyst argued the change of corporate culture at Apple may have been too much for the IBM veteran.

"At the end of the day, it might have been that he didn't have enough T-shirts and blue jeans in his closet," said Brian Marshall, an analyst with Gleacher & Company.

The iPhone 4's antenna is housed within the steel band that runs around the outside of the handset. This allows the phone to be significantly thinner than previous versions, but holding it so the bottom left-hand corner of the case is covered can cause the mobile reception strength to fall sharply.