* Second profit warning in a month
* Says faces further 35 mln stg dent to full-year earnings
* Shares fall up to 13 pct, down 54 pct this year (Adds detail, background)
LONDON, Oct 7 (Reuters) - Struggling British retailer SportsDirect cut its profit forecast for the second time in amonth on Friday, saying the latest slump in the pound could wipeup to 35 million pounds ($44 million) off its full-yearearnings.
Shares in the firm, 55 percent of which are owned by itsbillionaire founder and boss Mike Ashley, fell up to 13 percent,taking their losses so far this year to 54 percent.
The warning is the latest blow to a company trying to repaira battered image after it admitted to shortcomings in itsworking practices.
Its shares also plunged on the day after Britain's vote toleave the European Union, when the company said it had nothedged for moves in the pound against the dollar. Overnight,sterling dropped to a fresh 31 year low.
Last month, Sports Direct forecast core earnings of about300 million pounds ($373 million) for its financial year endingApril 2017, based on a pound/dollar rate of 1.30. It had made381.4 million pounds in its 2015-16 year.
The firm said on Friday that in light of sterling's recentweakness it had entered into a hedging arrangement with respectto the pound/dollar rate.
However, it said sterling's overnight fall resulted in a"crystallisation of that rate" at 1.19, resulting in a hit ofabout 15 million pounds to its 2016-17 core earnings forecast.
Sports Direct also warned that if the pound/dollar rateremained at 1.20 on average for the balance of its 2016-17 yearits core earnings would be hit by a further 20 million pounds.
At 1605 GMT, sterling/dollar was trading around 1.24.
($1 = 0.8035 pounds) (Reporting by James Davey; Editing by Kate Holton and MarkPotter)
