Specialty clothing retailer Gap Inc has seen its March comparable store sales fall 1%, after results were weighed down by its Old Navy brand and an earlier Easter.

Net sales increased 7% to US$1.56bn over the five weeks to 6 April, up from $1.46bn the same period last year.

The San Francisco-based retailer said the difference between the decline in comparable store sales and the growth in net sales is primarily due to the calendar shift of weeks in fiscal March 2013, compared to the same month last year.

Comparable store sales rose 1% at Banana Republic, but remained flat at Gap. Old Navy, however, posted a 2% decline in comparable store sales against an 11% increase last year.

"Overall, we're pleased with the month and are focused on selling our strong spring product to customers across all brands and channels globally," said chairman and chief executive officer Glenn Murphy.