By Ian Youngs
Entertainment reporter, BBC News
Music downloads are set to dominate the UK top 40 after record shops said they would agree new rules for digital hits.
Legal song downloads now account for 78% of all UK single sales
Downloads currently only count towards the singles chart from one week before the song is released on CD until two weeks after the CD is deleted.
That ensures music stores do not have gaps in their singles racks.
But the Entertainment Retailers' Association (Era) has said all digital sales should count and new rules are likely to come into force on 1 January.
Legal song downloads now account for 78% of all UK single sales - up from 23% two years ago.
Many singles are currently available to download several weeks before they are released on CD, often growing in popularity as their physical release approaches.
That means the change could see a return to songs climbing the charts as they gain momentum online.
This week's number one - I Don't Feel Like Dancin' by the Scissor Sisters - sold almost 45,000 digital copies before becoming eligible for the main chart, according to Music Week magazine.
Era secretary general Kim Bayley said the new rules still had to be ratified by retailers and record companies - who jointly control the charts.
But record shops have dropped their opposition to such a move in the wake of the digital boom.
"Era, like the other members of the Chart Supervisory Committee, believe that these digital sales should count towards the chart," she said.
"Era think it's fine and the chart should count those sales, provided we can get the message across adequately to consumers as to what's going on."
Shops would probably start using their own in-store singles countdowns to avoid having gaps on their racks, she said.
But fans should still be able to decide which format they want, she added, and digital and physical singles "should both be made available so far as possible at the same time".
A spokesman for the British Phonographic Industry - which represents record companies - said downloads had "transformed the way in which consumers buy music".
"If the singles chart is to remain the definitive list of the country's favourite songs, it has to reflect how music fans buy them," he said.
Many songs can be downloaded as soon as they appear on the radio
EMI chief executive Tony Wadsworth welcomed the move, saying the restrictions had been "holding the continued growth of digital sales back".
"Unfortunately, we're in this period of transition where there's a reluctance in some quarters to let go of the physical part of the single. That has resulted in some of these rules, which I just think are slowing us down," he said.
"A single can be made available for sale digitally as soon as it goes to radio and it's got a sales life which is not actually being represented in the chart until one week before a physical format is released, and that just seems absurd."
Mr Wadsworth added it was "frustrating" that a lot of people were buying single video downloads that also did not count towards the chart.