Ryan Harris fears Australia could ruin their chances of regaining the Ashes if they hand out more reprieves to England in the second Test at Lord's.
England batsman Jonny Bairstow was bowled by Peter Siddle while on 21, but replays revealed a no-ball and he went on to share a stand of 144 with centurion Ian Bell before the hosts ended day one on 289-7.
Steven Smith dismissed Bell, Bairstow and Matt Prior in the evening session as Australia ended on a high, but Harris, who picked up three wickets of his own, admits they cannot afford any more slip-ups.
"(Coach) Darren (Lehmann) is quite strict on that with us in the nets ... once we're off our long runs, we're not allowed to go over," said the paceman.
"There's no excuse for it. The line is there for a reason.
"It's not acceptable. It cost us a lot of runs today, and potentially ... it could cost the Ashes.
"Darren wasn't very happy. You just can't afford to (have to) take 11 wickets, or 12 wickets. It's as simple as that.
"It was probably the only one he bowled, but funny how it happened to be a wicket. That's how the game works."
Bell's innings of 109 was his third hundred in successive Ashes Tests, but Harris admits the Aussies had hoped he was out-of-form at the start of the series.
"We thought he was struggling coming into this series - he hadn't made a lot of runs," he said.
Bell made a patient start to his innings with England in trouble on 28-3 and Harris believes the Australian batsmen must display a similar approach.
"We spoke about our batters modelling themselves on him, and taking their time," he said.