Official music download websites could replace record shops as the public's preferred places to buy singles within five years, one of the UK's leading music industry figures has said.
Rock band Muse recently sold 5,000 copies of a song on the internet
The singles chart is under threat in its current form, Peter Jamieson, executive chairman of the British Phonographic Industry, which represents UK record companies, told BBC News Online.
Over-the-counter single sales are down 37% for the year so far compared with the same period in 2002.
The industry is hoping to revitalise the chart by launching a new top 40 that combines sales from approved websites with existing high-street figures.
The new chart could launch as early as the start of next year, Mr Jamieson said.
The demand for legitimate downloads will grow over the coming years and digital sales figures are likely to challenge those from shops, Mr Jamieson said.
"Don't ask me where, in five years time, it will end up - be it 50-50 or 60-40 in whichever direction," he said.
"But I see both of them as being significant businesses."
He also said the growth rate would depend on how much money the industry put into new services.
"But we are, as a music industry, responding to that consumer preference."
Mr Jamieson said: "It's our job to make sure that the charts are good, reflect popular taste and are a sensible marketing tool for the industry."
But they were currently under threat "because there isn't a good enough or strong enough download avenue".
Christina Aguilera came top of the first official download chart in April
They were also under threat because "the decline in physical singles sales is becoming more noticeable", he said.
Download sales would not make much impact on chart placings at the moment, Mr Jamieson said.
But recent online successes have given the industry evidence that such ventures can attract fans in large numbers.
An estimated 5,000 fans recently bought a new track by rock band Muse for 99p - nine weeks before the album was released, industry magazine Music Week reported.
That would have been enough to put the song in the "lower reaches" of the top 40.
Download services like Kazaa - where fans swap songs for free - would have to be eradicated "in due course", Mr Jamieson said.
"But I think you've got to grow viable legitimate alternatives so you can genuinely say to the consumer 'hey, stop stealing.'"
"It's got to be pretty easy for the consumer to do it properly before they will respond to you.
"I'm quite confident that once we have enough appropriate services out there, there will be - for all the right reasons - a drift towards them."
Christina Aguilera came top of the first official download chart, which tracked sales over two days in April.
Chart day change?
Other measures to breathe new life into singles sales are also being considered, Music Week reported.
Some within the industry want the new chart to be revealed on a Friday - rather than a Sunday - to boost weekend business.
There are also proposals to reduce the wait between a single first being played on the radio and being available to buy.
More two-track, cheaper CD singles are also likely to appear, while others are expected to be released as DVD singles to give fans more material.