There are mixed messages from the UK retail sector in the post-Christmas sales on Boxing Day after physical stores reported broadly flat footfall but online sales rocketed.

British consumers had held off before Christmas as they waited for the sales to take hold. This delay was a concern for nervous retailers who have struggled in recent years as falling incomes hindered consumer confidence and spending.

Retail data specialist Springboard said there was just a net 1% increase in footfall on Boxing Day compared to a year before, as a 9% decline in the number of town centre shoppers was offset by a 10% rise in those at shopping malls and retail parks.

"The footfall shows that people have headed out early - the Boxing Day sales are always a big event and people know to get out first thing and queue in order to find the best deals," said Diane Wehrle, marketing and insights director at Springboard.

"The initial spike in footfall is representative of that - but people on the high street may have headed home after getting what they wanted. The fact that shopping centres and retail parks are still up reflects the less onerous parking tariff that often deters shoppers from town centres."

Research by IBM shows online retail sales in the UK jumped 40.4% on Boxing Day against a year before, with more and more consumers using mobile devices to shop on the internet. Mobile accounted for 58% of all retail web traffic, up from 42% in 2012.

"This is the first time that traffic on mobile devices has outstripped the PC," said James Lovell, a smarter commerce retail solutions consultant at IBM.

"Mobile has rapidly become the dominant channel and now retailers really need to look at the role that each device is going to play within the overall customer journey and decision making process.

"The key challenge will be how they maximise the effectiveness of these devices to help augment the in-store customer experience as well as the traditional digital only channels."

IMRG, the trade body for online retailers, predicts UK consumers to spend £472.5m on Boxing Day internet shopping alone.