Heinz has been forced into an embarrassing rethink after a wave of customer complaints over its much vaunted lightweight tomato ketchup bottle.

The company launched the bottle in April, heralding it a major step forward in packaging reduction. Made from clear plastic and 9% lighter than its predecessor, it would save 340 tonnes of plastic a year, Heinz boasted.

However, it emerged this week that the bottle had a defect that made it brittle and difficult to squeeze.

"Very occasionally, over a period of time, if the bottle has been dropped, the various layers of plastic can take on a slight pearlescent appearance and the bottle may not be quite so squeezy," said a Heinz spokeswoman. "There is no loss of protective barrier and the quality of the ketchup is unaffected. A further bottle enhancement being introduced will eliminate the occurrence."

The manufacturer is developing a replacement after receiving a barrage of consumer complaints. A new bottle would be rolled out in the next few weeks, added the spokeswoman.

The glitch has caused a storm on consumer website MoneySavingExpert.com. One poster claimed to have purchased two of the bottles, both of which were affected, writing: "Once two thirds of the sauce was used it was impossible to squeeze out the rest."

The problem is a setback for Heinz, which has made much of its sustainability credentials. It was the first branded supplier to sign up to the Courtauld Commitment, and its work on the ketchup bottle has been highlighted as one of the Commitment's biggest successes thus far.