Britain's biggest sporting goods retailer Sports Direct employs around 75 percent of its 19,000 UK workers on much criticised zero-hour contracts, its chairman said on Wednesday.

Answering questions from a British parliamentary committee over its employment practices and the administration of part of one of its fashion businesses, Sports Direct Chairman Keith Hellawell admitted some 15,000 UK staff were on zero hour deals, which do not specify set working hours or guaranteed income.

Sports Direct, whose 4,300 permanent UK staff qualify for lucrative bonus share scheme payouts, had previously refused to confirm how many of its workers were on the contracts.

Hellawell told the Scottish Affairs Committee the approach offers flexibility for its largely young workforce, some of whom are university students, and allowed the firm to meet demand.

However, Sports Direct is engaged in legal challenges with some long-serving zero hour staff who claim they should be included in its generous bonus share scheme.

Nearly 700,000 people are on zero-hours contracts in their main job, according the UK's Office for National Statistics, a growing figure that has attracted increased political scrutiny.

Hellawell said Sports Direct was looking at the potential future for zero hour contracts but warned that any switch to permanent contracts would result in higher costs and less jobs.

Much had been made of Hellawell's appearance before the lawmakers, who had pushed for Sports Direct's fiercely private executive deputy chairman, founder and major shareholder Mike Ashley to attend, only to be told he was not available in March.

Hellawell said Ashley would be willing to face lawmakers.

Hellawell was also asked to explain its handling of workers at its fashion arm USC's Scottish warehouse, who were made redundant in January when administrators were called into a Sports Direct-controlled business that owned 28 USC stores.

The stores were bought out of administration a day later by another Sports Direct fashion unit, Republic, and continue to trade but workers at the Ayrshire warehouse were given just 15 minutes notice before they lost their jobs.

Hellawell said the administration, sparked by demands for payment by Diesel, one its suppliers, had left no time to consult with warehouse staff, despite lawmakers saying Sports Direct's CEO had been talking to administrators since November.

Hellawell said he and the Sports Direct board only decided to put the business into administration on Jan. 12.

Sports Direct operates over around 700 sports stores across the UK and Continental Europe, employing 28,000 staff in total.