Uber said on Tuesday that treating its British drivers as workers, entitling them to rights such as the minimum wage and holiday pay, would add tens of millions of pounds to the taxi app's costs. Uber currently classifies its around 50,000 drivers in Britain as self-employed, affording them only basic entitlements. "I don't have the precise figures . but I'm certain it would be the tens of millions certainly," the firm's UK Head of Policy Andrew Byrne told parliament's business committee. Also appearing before lawmakers, Deliveroo's UK and Ireland Managing Director Dan Warne said additional costs including National Insurance contributions, would add around 1 pound ($1.32) to the cost of each delivery. Firms operating in the so-called gig economy - whereby people tend to work for different companies without a fixed contract - have been criticised by unions and some lawmakers for what they call exploitative practices. Uber and Deliveroo both say their drivers enjoy the flexibility they offer but last year two drivers won a tribunal hearing against Uber and were granted working rights, in a decision which the Silicon Valley firm appealed last month. Uber's Byrne said on Tuesday he expected the judge to make a ruling by around Christmas.