Sales of electronic cigarettes (e-cigs) through traditional stores - including convenience and CTNs - are flatlining as adult vapers switch to buying online and through the UK’s growing number of specialist e-cig stores.

Following a rapid acceleration in the past two years, sales through traditional stores have now plateaued, reaching just under £10,000 a week in October - almost no change from March, data from a recent Nielsen webinar showed.

More than 2.1 million people are now thought to use e-cigs on a regular basis, but almost half (45%) of e-cig sales are now being made online, with internet sales likely to accelerate in 2015 as manufacturers place more emphasis on loyalty schemes, Nielsen UK tobacco analyst Natasha Kendall said.

There are now also more than 600 specialist e-cig shops operating in the UK and that figure is also growing month on month.

Last month e-cig brand VIP opened its first shop in East London’s Westfield Stratford City shopping centre. The ‘Blending Boutique’ allows vapers to blend their own e-liquids, while the latest technology can be trialled in a dedicated ‘luxury lounge’.

Convenience retailers keen to grow their e-cig sales in the face of growing online and specialist competition should seek to hit a variety of different price points and improve their product knowledge, Kendall said.

They should also focus on expanding their ranges with a wider variety of tank devices and flavour options, she added.

The most popular e-cig flavour is tobacco, closely followed by menthol and berry flavours - a trend which is being mirrored in key fmcg categories such as cider.

Four in five e-cig users now vape on a daily basis, while 24% of vapers do so 10 or more times a day.

The past year has also seen a growth in e-cig advertising via a wide variety of mediums. TV was the most popular at 34%, followed by press at 28% and outdoor at 25% in 2014.