A fall in subscription numbers has been one of the key reasons behind Austar United Communications Ltd (ASX:AUN) disappointing first half results.

The pay TV company reported a 41 per cent drop in first-half profits yesterday, to $20.7 million.

In the six months ending on June 30 Austar added 3389 customers – less than half the number expected.

The number of renewals fell despite the introduction of the digital video recorder MyStar.

The company’s bottom line has also been hurt by derivative losses after the previous first-half results were boosted by a $21.7 million one-off gain on interest rate swaps.

Austar chief executive, John Porter says that subscriber growth has continued to be a challenge in Australia during the financial crisis especially as government stimulus ended and interest rates were increased.

Austar reported a profit of $58.78 million for the year ending 30 December 2009.