British Telecom is facing stiff resistance from its union over a move to open a call centre in India to manage its directory inquiry services.

While BT  said it would not be closing any existing call centres in Britain and that any job losses would come from the high levels of "natural wastage" in the call centre industry, the communication workers union said BT was planning to transfer 700 jobs to India.

The union said it had written to 3,500 BT workers urging them to resist the move "by all means possible."

"We would stress that whatever decision is reached we would not destroy BT jobs in the UK, only to recreate them in India," a company spokesman said in London.

If BT plans go ahead it will become the latest in a group of companies to take advantage of India's cheaper employment costs.

This month Aviva, Britain's largest insurer, announced that it would shift 1,000 back-office jobs to India by the end of the year. Other companies to have already made the move include HSBC and Prudential.

BT, which has suffered from flat revenue growth, said that the company was considering whether or not to establish call centres in India. However, "a final decision is yet to be taken," the spokesman said.

BT has about 2,500 staff in Britain many of them on temporary contracts who handle hundreds of millions of calls made to its directory inquiry service every year.