'There are improvements to be made with regards to DRS'

England coach Andy Flower allowed himself a rare smile after his side retained the Ashes but the decision review system is prompting headaches and he wants the authorities to sort it out.

The tough taskmaster does not tolerate ordinary from his team and the performance of the decision review system (DRS) in the drawn Old Trafford test was far from satisfactory.

Australia's Usman Khawaja was given out in the first innings by the on-field umpire and third umpire despite no evidence he touched the ball while Kevin Pietersen did appear to nick behind in England's second innings but Hotspot failed to pick it up.

"Firstly umpiring is a very tricky business but I would say that there are very clear protocols to use and to stick to and I think some calm decision-making needs to be made over the next two tests," he told reporters.

"I think there are improvements that can be made. There are improvements in the use of the technology and the use of experts who know how to use the technology that could make a difference to getting better results."

The holders will keep the urn as they are 2-0 up with two to play after Monday's stalemate in Manchester, with Flower believing hard work was key rather than the rain which wiped out the last two sessions as Australia scented victory.

"Retaining the Ashes is important of course and I'm very proud of the team and the team are obviously proud after a hard-fought test, a hard-fought three tests to be in this position. But we do want to go on to Durham and win up there," he said ahead of the fourth test starting on Friday.

"I thought the fight and resilience and character that we showed in that first innings is the reason why we drew this test."