Ocado has warned its profits are likely to be hit because to capacity problems at its warehouse.

The online grocer said “capacity constraints” and “production issues” at its Hatfield depot have undermined profit margins in the fourth quarter.

Ocado said earnings were expected to be in the range of £27.5m to £28.5m in the year to November 27, compared to £22m in 2010.

Gross sales were approximately £643m for the full financial year, up 16.7% on the previous year.

Ocado has employed additional labour at Hatfield distribution centre to process more orders.

The retailer said it remains focused on providing a “superior service”. For the full financial year, 98.3% of items were delivered as ordered and 92.3% of orders were on-time or early for their one hour delivery slots.

Construction of Ocado’s second depot in Warwickshire “remains on-time and on-budget”, the retailer said. Capital expenditure for the financial year is lower than expected, in the range of £125m to £130m, due to the timing of capital expenditure payments.

Ocado chief executive Tim Steiner said: “We are encouraged by the operational capacity improvements that we have made, but are disappointed that we did not achieve as large or as early an increase as we had originally planned.

“There is more work to be done and we are focused on delivering capacity and sales growth in the first half of 2012.”

The group’s full year results will be released on January 31, 2012.