Footwear giant Clarks has delivered a record first half under new chief executive Melissa Potter, but has struggled in the UK and remains cautious about future trading.

Clarks’ pre-tax profits soared 111.2% to £45.2m in the six months to July 31, largely driven by its US business. Revenue jumped 5.7% to £577.2m. Potter, who took over from Peter Bolliger in May, said that its North American business, comprising 200 outlets, enjoyed a “striking turnaround in its fortunes” following a difficult 2009.

She said: “Of all the parts of our worldwide business Clarks Companies North America suffered most during the recession, and this is also where our performance has bounced back with the greatest vigour.” US turnover grew 18.7% to $315.5m (£201m).

However, Clarks’ UK retail division - which comprises about 500 stores - had “battled to hold its own” in the face of continued soft market conditions and fragile consumer confidence, she added. Potter declined to split out UK figures but added the domestic arm was also affected by reduced footfall and discounting among its competitors.

Potter predicted UK retail growth would be challenging over the coming months and said Clarks would need to work on differentiating its product and service proposition.

Clarks chairman Peter Davies said the retailer planned to “keep trying to do what we do better” through improved service and shopping environment.

Ecommerce sales rocketed 70% to £13.1m in the period. The retailer plans to expand its multichannel business into new European countries early next year and aims to increase its number of franchise partners to open more stores.

Last month Clarks kicked off a trial of a new store format in UK and overseas locations including Exeter, Glasgow and Amsterdam. Davies declined to comment on the details of the refit until the company has seen how consumers reacted to the changes.

Potter joined Clarks in 1998 as a graduate trainee and held various roles including managing director before she was named chief executive.