More than nine out of ten first-class letters are being delivered on time, the best figure for five years.
The Royal Mail praised its employees for working hard to deliver better results, but chief executive Adam Crozier warned the threat of strikes was undermining customer confidence.
Consumer watchdog Postwatch welcomed the improvement in first-class deliveries but said the service was still underperforming, with a million letters not reaching their destination the next day.
Chairman Peter Carr said: "Royal Mail is likely to struggle to meet the majority of its targets this year even without a strike."
The Royal Mail said 93.2% of first class letters were delivered on time in June, the highest figure since the summer of 1998.
Mr Crozier said the improvements would be "thrown away" if postal workers went on strike in a dispute over pay.
The Communication Workers Union is balloting 160,000 workers on whether to take industrial action after peace talks broke down on Wednesday.
Friday August 29, 2003
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