Ocado is gearing up to push the button on its plans for a £1bn stock market flotation this week, it is understood.

The online grocer is expected to reveal that underlying profits have doubled from more than £2m to £4m-£5m in the first half of its financial year, according to the Sunday Times. Sales are expected to be up by more than 30%.

Ocado – which delivers Waitrose products – is expected to make a formal announcement this week of its intention to float. It is then expected to make its stock market debut next month.

Ocado is to offer customers who have spent more than £300 since the start of the year the chance to buy shares in the float. It is thought the retailer hopes its shoppers could buy up to 20%.

The listing is however controversial as Ocado has not yet made a pre-tax profit in its 10-year history. If successful, the float will fund a new distribution centre and wipe out the grocer’s debt.