THE UK’s most popular online bingo site has invested £1m to overhaul its office following a 50% increase in technical staff over the past year.

Sunderland-based Tombola will now occupy the entire five-storey Wylam Wharf building on the city’s riverside after growing its product development team from 31 to 55.

The move comes after accounts revealed the company’s turnover had shot up by 21%, reaching £26.8m for the year ended April 30, 2011.

This jump in revenue figures has been helped by the meteoric rise of the smartphone and other handheld devices, which have allowed Tombola’s customers to play anytime, anywhere.

Head of marketing, Dawn-Elizabeth Howe, said: “We’ve really developed our mobile and tablet technology and the two games that we have on there at the moment are performing extremely well.

“At 9pm, which is widely regarded as peak playing time, we generally have around 6,000 players, whereas our competitors will be lucky to draw 1,200 at the same time.

"We are much bigger and performing a lot better than many of our competitors.

“Five years ago we had a dozen people in the development team, whereas we have 40 now, which just shows how much we are investing in the development of our games in-house.

“At one point this year, we were recruiting a member of staff for the development team once a week, but that’s scheduled to slow down as we’ve pretty much filled all five floors of the office.”