MySale has warned it expects to post a first-half loss amid “challenging” trading conditions.

The discount fashion website said in a pre-close trading update that it was forecasting an underlying EBITDA loss of A$5m (£2.72m) in the six months to December 31, 2018. It registered a A$5.5m (£3m) profit during the same period the previous year.

MySale, which counts Sir Philip Green and Mike Ashley among its shareholder base, said group revenues tumbled 17% to A$126m (£68.9m) during the period. Gross margins were also dented, slipping from 30.2% a year ago to 23.4%.

The Australian business blamed the slump in sales and profits on the “market disruption” sparked by changes to goods and service tax (GST) regulations in its domestic market.

It added that “product mix and inventory issues”, plus a reduction in its offline activities during the period, had also impacted performance.

However, MySale insisted that its full-year results would be “in line with market expectations” despite the turbulent first half.

The etailer said it was accelerating its cost savings programme, improving its product mix and increasing local sourcing in order to boost its margins in the second half.

MySale boss Carl Jackson said: “While performance during the first half of the year has been disappointing, we have taken immediate action to address the issues.

“Our previous plans to streamline and automate the business have been accelerated and these actions are already delivering results. The changes to product strategy are materially under way and will be completed in the second half.

“While we have experienced a short-term dip in revenue and profitability, we anticipate the actions initiated will deliver a positive underlying EBITDA in the second half and for the full year.”

MySale will post its interim results next month.