A battle for control of a Bradford chemical plant continued last night as a buyout of Ciba by German giant BASF was blocked by a major shareholder.

The investment by BASF was approved by Ciba’s directors, which recommended shareholders accept an offer which equated to a premium of just over 32 per cent on their closing price on Friday.

However, asset management company Bestinver, which holds a 13.2 per cent stake in Ciba, said it was unhappy with the valuation.

That cast doubt on suggestions by BASF, the world’s biggest chemicals company, could open new doors to the Low Moor plant’s products, which are used in papermaking, mining, oil extraction, wastewater treatment and textile processing.

A spokesman for the Bradford site, which has 850 staff, said the takeover bid was still at an early stage, and it was not yet clear what the future held for each part of the Ciba empire, which employs 14,000 people at 63 sites in 20 countries and research centres in 12 countries.

“Ciba will be fully integrated into BASF structures, but it is far too early to be more specific,” the spokesman said.

Plans to modernise the Low Moor plant during 2009 include a new powder production line and a second liquid product line.

BASF executive board chairman Jurgen Hambrecht said Ciba’s expertise in producing water treatment chemicals – a role of the Bradford plant – was a major attraction.

He said: “With the acquisition of Ciba, we are strengthening our portfolio and expanding our leading position in speciality chemicals with products and services for a variety of customer industries, in particular the plastics and coatings industries, as well as water treatment.”

BASF said in a statement that it is eager to develop Ciba’s presence in niche markets such as mining, an industry in which demand has remained strong for Bradford-made products.

“Ciba’s businesses for attractive markets such as oil and mining would benefit from wider market access and BASF’s extensive application and product know-how,” it said.

However, BASF also believes there is a need for some restructuring in chemicals for paper treatment – an area which saw a drop in sales of eight per cent in the first half of the year for Ciba due to a fall in demand by the European paper industry.

“In paper chemicals, we will intensify the urgently needed restructuring process and become the world’s leading supplier, with an extensive portfolio,” Mr Hambrecht said.

The decision by CIBA’s board to back the sale came on the same day as BASF was named as the world’s biggest chemical company ICIS Chemical Business magazine.

The German company topped the ratings with $85bn (EUR61bn) in sales in 2007, boosted by the 2006 acquisitions of US-based catalyst and speciality chemical firms Engelhard and Johnson Polymer, and Degussa’s construction chemicals business, based in Germany.

BASF’s offer is subject to an acceptance rate of at least 66.6 percent of the voting rights.