Transport company PD Logistics, in Billingham, shed 30 jobs earlier this month, blaming a downturn in chemical production on Teesside.

In March, Eastman Chemicals moved production to the US and closed its plant in Hartlepool with the loss of 75 jobs.

Following the latest round of redundancies at Invista, which manufactures Lycra and nylon, questions are being raised about the sustainabity of Teesside's chemical industry.

Experts agree it is a serious issue - the chemical industry, along with biotechnology and pharmaceuticals - accounts for a quarter of the region's gross domestic product, and 37 per cent of the North-East's expertise is tied up in the sector.

According to regional development agency One NorthEast, more than 35,000 people are directly employed in the industry and 40 per cent of the region's research and development is carried out by the sector.

Last night, a statement from Invista said it hoped to secure its long-term future at Wilton with a cost-cutting strategy.

It said: "The cost-reduction efforts are being made to allow the Wilton facilities to be more competitive.

"Invista's business has been impacted for some time from escalating raw material costs and other market trends that cause the business to execute strategies that will increase the health of the business."

Ian Click, chief executive of the Teesside Chemical Initiative, said the move was necessary to increase productivity and reduce costs, for the sake of the long-term sustainability of the business.

He said: "Invista is not shutting down any of its plants or reducing its activities.

"The company needs to make sure the business has a competitive future, and the same goes for the other chemical companies on Teesside.

"In terms of Teesside, it should make its future more secure here rather than less. It is an uncomfortable message that people have had to lose their jobs for that to happen.

"But competing against companies in countries such as China, where it costs only one-twentieth to employ someone as opposed to the UK, the Teesside chemical industry has to be better technically as well as very competitive in terms of use of manpower."

Alistair Russell, who specialises in developing leadership and management in large corporate organisations at the Durham Business School, said: "I see Invista's move as an example of the chemical industry in Teesside reacting early to a global situation which will be sustained.

"It is very much about the industries responding and being adaptive and flexible and keeping ahead of the game.

"There is a huge knowledge capital on Teesside which is being sustained, as long as the companies keep ahead of global competition.

"The chemical industry does need to continue changing and developing and adapting."

Alistair Arkley, chairman of the Tees Valley Partnership, said the region's chemical industry, which represents about half of the UK's chemical operations, needed as much help as possible from the Government and Europe to support it.

He said: "The chemical industry is absolutely critical to the economy in the southern part of the region and it is vitally important it remains competitive. I know there are issues about the cost of shipping raw materials and I think it is vital that as much help as possible is given to help sustain the industry."