The ESB and British Telecom are to unveil plans for their joint venture telecommunications company today. It is expected that the new company will target the corporate market initially.

The companies will announce the make-up of the board, the amount they expect to invest and how quickly they will roll out the service.

However, the name of the new company - understood to be Ocean - will not be unveiled officially until later this month.

British Telecom is taking a 50 per cent stake. The ESB, through ESB International Telecommunications, has taken on a partner as part of its 50 per cent - US insurance company, AIG, which will have a 20 per cent holding in the venture.

The ESB's investment over about five years is expected to be £27 million. However, sources said last night that it was likely the new company would announce an increased investment plan - the original sum pencilled in was £130 million over 10 years. If the joint venture company wants to target the residential market, the attractiveness of which has been boosted by the bringing forward of the abolition of Telecom's derogation by one year, substantially more investment will be needed.

Some sources said yesterday that the ESB board was reluctant to put up a lot of money and so had opted to take in another partner to spread the risk. The current ESB system is mainly radio-based and has capacity up to about four megabytes, according to industry sources.

It is expected the investment will be used to upgrade the existing network to cope with the demand of multiple business users throughout the country.