Shareholders in heart valve maker Aortech were stunned again yesterday as the company reported it was in legal dispute with its biggest customer, giant US corporation St Jude Medical.

Cash-strapped Aortech, the AIM-listed group which migrated in 2004 from Lanarkshire to Australia and thence last year to the US, put itself up for sale three months ago.

Investors had until recently hoped that St Jude, which incorporates one of Aortech's materials into its products, might be among potential buyers for the group's assets. But at the end of last month Aortech reported that no offer for the entire group was likely.

Yesterday the group, chaired by former Edinburgh invest- ment banker Bill Brown, warned shareholders that it had issued St Jude with a rectification notice following alleged "serious breaches" of its agreement for licensing and supply.

The board believed the breaches were not capable of cure within the 30-day rectification period, and had therefore voted to terminate the agreement with St Jude.

The US group would "continue to own the necessary assets to manufacture polymers but will no longer have the rights in the company's intellectual property and knowhow to manufacture the proprietary AorTech materials".

The shares, at 157p early last month, dropped 4p to 51p.