UK supermarket Asda loses latest round of equal pay case

* Court of Appeal upholds ruling on Asda workers

* Asda to apply to Supreme Court to appeal judgment

* Case about different pay for store and distribution centre staff

LONDON, Jan 31 (Reuters) - British supermarket chain Asda, which is owned by Walmart, has lost a challenge at the Court of Appeal in the latest round of a long-running dispute with staff over equal pay for different roles.

Law firm Leigh Day, which is representing 30,328 Asda workers, said on Thursday the Court of Appeal upheld an earlier ruling that Asda store staff can compare their roles with those in distribution centres.

The store staff argue they should have parity with better paid workers in the distribution centres.

Leigh Day said the ruling means the claim against Asda can now progress to the next stage - assessing whether store and distribution centre roles are of equal value.

The firm said in total it is representing over 35,000 shop floor staff at Britain's big four supermarkets – market leader Tesco (Frankfurt: 852647 - news) , Sainsbury (Amsterdam: SJ6.AS - news) 's, Asda and Morrisons - in equal pay cases which will be impacted by Thursday's judgment.

Leigh Day said its total estimate of the claims against the big four, if they lose their cases, and are ordered to pay all eligible staff could be over 8 billion pounds ($10.5 billion).

Asda said it was disappointed with the decision and would apply to the Supreme Court to appeal the judgment.

"We remain confident in our case. This appeal has caused no delay to the main case, which has been continuing in the Employment Tribunal.

"The tribunal has yet to consider whether the jobs are of equal value in terms of their demands; it is only if some jobs are of equal value that the tribunal will go on to consider the reasons for the pay differential between them."

Asda said pay rates in stores differed from those in distribution centres because the demands of the jobs were different.

"They operate in different market sectors and we pay the market rate in those sectors regardless of gender," it said.

Last April Asda agreed to be taken over by Sainsbury's in a 7.3 billion pound deal. The deal is currently being probed by Britain's competition regulator. (Reporting by James Davey Editing by Keith Weir)