England coach Andy Flower joined the captains of both sides in calling for improved use of the Decision Review System (DRS) in the remaining two Ashes Tests against Australia.

Holders England retained the Ashes after the third Test at Old Trafford ended in a rain-affected draw on Monday, leaving the home side 2-0 up with two to play ahead of the fourth Test in Durham starting on Friday.

But once again the use of DRS by the officials this Ashes was a major talking point after yet more contentious rulings in Manchester.

"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," Flower said Tuesday.

Sometimes the available technology has contradicted itself and former Zimbabwe batsman Flower added: "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."

Given eight of the International Cricket Council's 12-strong elite panel of umpires are barred from officiating in Ashes matches because they are from either England or Australia, this series has been overseen by the quartet of Pakistan's Aleem Dar, Sri Lanka's Kumar Dharmasena, New Zealand's Tony Hill and South Africa's Marais Erasmus, who've rotated the standing and third umpire roles between them.

In the first Test at Trent Bridge, where Erasmus was widely criticised for overturning Dar's original not out decision and ruling England batsman Jonathan Trott was out lbw, six out of 13 reviews led to a changed decision.

At Lord's, where England won the second Test by 347 runs, only one review led to an overturned call.

Meanwhile at Old Trafford, where Hill and Erasmus were the men in the middle with Dharmasena the third umpire, the teams sought 10 reviews, with none of the standing umpires' decisions reversed.

This appeared to indicate the teams were becoming progressively more careless with their challenges, when further exposure to DRS ought to produce the reverse effect, or that the third umpire was increasingly reluctant to over-rule his two standing colleagues.

At Old Trafford, there were times when both England and Australia, more than being frustrated at DRS verdicts going against them, didn't seem to understand why their challenges had failed.

In Manchester, the most controversial case involved the first innings dismissal of Australia batsman Usman Khawaja, given out caught behind off the bowling of off-spinner Graeme Swann for one by Hill.

DRS appeared to indicate there was no noise at the moment the bat ought to have hit the ball and nor did Hotspot reveal an edge.

Yet Dharmasena upheld Hill's decision, prompting Australia great Shane Warne to label the decision "absolutely shocking".

Meanwhile both Australia captain Michael Clarke and England counterpart Alastair Cook said they were "confused" by the application of DRS this series.

"I'm a fan of DRS, I am a fan of technology in our game and there's obviously been a couple of occasions where both teams have been a bit confused but the one thing I like about is that it is consistent for both teams," said Clarke.

Cook added: "In practice, DRS has worked really well, maybe apart from this series.

"I don't know whether it's just because it's the Ashes the cricketing gods have thrown up some slightly inconclusive evidence.

"We are just a little bit confused at the moment why certain decisions have been overturned and certain decisions haven't been overturned.

"I don't think that's just with an England cap on, I think both sides would be feeling that.

"We are a little bit confused with it but hopefully the ICC can iron out (the problems) and we can get back to what it's designed for which is making more decisions correct."

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