The boss of Ocado has hailed a "transformational period" as half-year revenues soared to almost £800 million - but the listed company fell into the red with a pre-tax loss of £9 million.

Ocado posted group revenue of £799.9 million for the 26 weeks to 3 June 2018, up more than 12 per cent from £713.8 million in the first half of 2017.

However, it recorded a loss before tax of £9 million for the period, compared with a profit of £7.7 million a year earlier.

The company warned that its profits will dip in 2018 after a major investment in its UK logistics hub and its technology platform.

"This is a transformational period for Ocado," said chief executive Tim Steiner.

"We have developed unique and proprietary technology to offer retailers an end-to-end operating solution for grocery retail that enables them to meet the changing needs of consumers."

Steiner added that the success of the firm's tech platform continues to be demonstrated by its UK retail business, where Ocado "continues to outpace our competition in terms of our service offering and our growth".

"We have just opened our latest state-of-the-art Customer Fulfilment Centre, which, once at full capacity, will be the largest automated warehouse for online grocery retail in the world and will showcase the scalability, adaptability and efficiency of our platform," he said.

During the 26-week period, Ocado hired more than 150 new software and hardware engineers, taking the total number of technical experts working on its platform from nearly 1,400 to over 1,550, with this expected to grow further in the second half of the year.