Nov 12 (Reuters) - Sales of Dr Martens signature boots sank during an exceptionally hot summer, dragging first-half revenue lower and widening losses, the company said on Thursday, warning that the holiday shopping season would be decisive for its full-year results.

The uncertain outlook knocked shares in the British bootmaker 15% lower by 0815 GMT.

The disappointing half underscores the challenge facing Chief Executive Ije Nwokorie, who is attempting to wean Dr Martens off discounts and broaden its appeal beyond boots against a tough economic backdrop for consumers.

Winter trading will be decisive, the company said, with the Black Friday weekend and the run-up to Christmas crucial to whether boot sales recover enough to bolster full-year results.

Analysts expect adjusted pretax profit of £65.7 million ($87.1 million) on revenue of £777 million for the year to March, according to a company-compiled consensus.

But Dr Martens said that, at this point, there was a wide range of outcomes for full-year sales and profit.

Its reported adjusted pretax loss widened to £13.7 million in the six months to September from £9.4 million a year ago. Revenue for the period dropped 9% in constant currency to £290.4 million, with the UK slumping 21% and the US slipping 5%.

"We lessened the impact on profit from the revenue decline with good gross margin performance and continued tight cost control," Nwokorie said in a statement. "Trading in the key weeks ahead will be crucial to determining our full-year outturn."

Performance in the second quarter deteriorated versus the first and the UK market saw a bigger-than-expected fall in revenue, the company said.

($1 = 0.7543 pounds)

(Reporting by Yadarisa Shabong in Bengaluru; Editing by Jochelle Mendonca and Joe Bavier)

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