The floor coverings firm, which has 313 UK stores, said like-for-like sales declined by 1.9 per cent in the 13 weeks to July 2, compared with a 1.2 per cent fall a year earlier.
Shares opened seven per cent lower as Topps said it did not expect any material change to trading conditions over the final quarter of its financial year.
Analysts have warned low levels of housing transactions and consumer confidence remain a drag on short-term prospects, while DIY chains have stepped up their battle for market share.
Topps said: “The business will continue to focus on achieving the efficiencies necessary to drive improved gross margins which will help to offset some of the impact of the challenging environment.”
In June, Topps reported adjusted profits of £7.2m for the 26 weeks to April 2, against £7.8m during the equivalent 27 week period a year earlier.