LONDON, Sept 21 (Reuters) - British clothing and footwear retailer JD Sports Fashion (JD.L) posted a 36.5 percent rise in first-half profit, boosted by the soccer World Cup, and said trading in the second half had got off to a solid start. "The result for the full year remains very dependent on the sales and margin performance in December and January," the firm said on Tuesday.

JDSports.co.uk

The group, which trades as JD Sports, Chausport, Size, Bank and Scotts from over 530 stores, made an underlying pretax profit of 19.4 million pounds ($30.3 million) in the six months to July 31, up from 14.2 million in the same period last year.

Group revenue increased 18.5 percent to 383.9 million pounds, with the gross margin up 20 basis points to 48.2 percent.

Sales at UK and Ireland stores open over a year rose 2.8 percent over the half and were up 2.7 percent for the four weeks to Aug. 28.

The firm, which ended the period with net cash of 34.5 million pounds, is paying an interim dividend of 3.8 pence, up 15.2 percent.

Shares in JD Sports have increased by nearly a third over the last year, outperforming a 1.5 percent fall in the general retailers index .FTASX5370

The stock closed at 726 pence on Monday, valuing the business at 353 million pounds.

(Reporting by James Davey, editing by Mark Potter)