Shares in National Grid were down on the FTSE 100 in morning trading, despite the group reporting a strong rise in pre-tax profit in the half year ended 30 September.

The group said that earnings increased 18 per cent to £656 million, while pre-tax profit rose 45 per cent to £938 million.

National Grid added that it would be raising its interim dividend eight per cent to 12.90 pence per share.

Capital Investment in the period rose by £122 million to £1.7 billion, while net debt fell £2.9 billion to £19.2 billion thanks in part to a rights issue raising £3.2 billion.

Steve Holliday, Chief Executive, said, "I am pleased with our operating and financial performance in the first half of the year. Operating profits were up 31% on last year. This is driven by strong performance in all our businesses and the continued growth of our asset base. This period's profit growth is additionally driven by timing impacts, as we had a significant under-recovery of revenues in the first half of last year. In line with our policy, we are increasing the rebased interim dividend by 8%. We are making steady progress in the US with our process of filing for required improvements in our various rate plans and we await the outcome in New York.

"We have increased our capital programme, investing where we are confident we can earn attractive returns. We welcome the announcement of the new RIIO regulatory regime in the UK with the focus on investment and innovation. We are already benefitting from the current incentive schemes and expect to see more of these under RIIO. We are confident that our strategy will continue to deliver essential changes in our energy landscape while creating significant value for shareholders and wider stakeholders".

By 11:30 shares in National Grid were down 1.37 per cent on the FTSE 100 to 576.50 pence per share.