Stereophonics have scored the UK's biggest download hit of the year so far

Download music is due to be merged into the official chart later this month.

But some independent labels fear that the dominance of Apple's iTunes in the UK market may favour major labels.

The Association of Independent Music said it had written to the Official Charts Company (OCC) to postpone the launch on 17 April.

It said some labels are concerned that the chart will be skewed in favour of artists represented on Apple's download service iTunes, which has an 80% share of the UK download market.

The Association is concerned that independent labels do not yet have a large enough repertoire on iTunes.

Looking at this week's midweek download chart, the indies have in fact outperformed the majors British Phonographic Industry

However the British Phonographic Industry (BPI) insists more independent labels are getting their music on major online websites.

The organisation has beeen running a campaign to get more indies online in the run-up to the launch of the new chart.

It said only one of the 17 independent singles in this week's singles chart was not available as a download on the UK's three leading digital music services - iTunes, Napster and OD2.

'Long way'

A spokesman added that the Stereophonics -who are on an independent label - have scored the UK's biggest download hit of the year so far.

Conversley, Tony Christie's hit (Is This The Way To) Amarillo was the top-selling single in shops for the same period - but failed to figure in the download list

Figures from the OCC, who will produce the chart - showed that, in tests, independent label records fared better in this week's merged singles chart, against the physical chart.

Comedian Peter Kay is currently top of the singles chart

There were nine independent titles in the combined chart, against eight in the physical chart, but the BPI did admit there was still a "long way to go".

"No one is pretending that indie representation on the download platforms is as good as it could and should be, and there is a long way to go," a BPI statement said.

"That said, it's simply not true to suggest that indie representation on the charts is an issue ahead of the chart merger.

"In fact, looking at this week's midweek download chart, the indies have in fact outperformed the majors."

The statement added that the BPI had run seminars, published an online guide for independent labels and urged all the digital music services to fast track indie singles.

The inclusion of downloaded music in the official singles chart has already been delayed for a month.

The BPI had originally planned to include download formats in the chart from 20 March, but the date was put back to create a "level playing field" for independent labels.