RBS has ruled out holding a new poll to find out who will grace its new £10 note, while it investigates possible fraud.

Mary Somerville, who would have become the first woman on an RBS banknote other than the Queen, was on track to top the poll when a late surge for Thomas Telford saw him race into first place as voting closed.

Bank officials suspected deception as the engineer, dubbed the colossus of roads, went from a dismal third place with 500 likes to win the race with 5,100 votes, apparently accruing thousands of supporters in just a few hours.

Former frontrunner Mary Somerville, the mathematician and astronomer, had gradually built her 4,300 votes over the full week of the ballot.

Members of the public had been asked to vote for one of the three shortlisted candidates by liking their picture on the bank’s Facebook page.

Third-placed candidate James Clerk Maxwell, a theoretical physicist, won 2,100 votes when the totals were tallied at the close of the ballot at midnight on Sunday.

RBS insists its website was not hacked but has handed information from its Facebook page to the social media giant to investigate.

The bank said it will not rush the investigation and wants to ensure all votes were valid before announcing the winner of the poll.

An RBS spokesperson said: “As a result of one of the candidates attracting a high volume of votes in a short space of time, we are looking to establish if these votes were genuine. We will announce the new face of the £10 note as soon as we can.”

IT experts believe “swarming” or “brigading” may be behind Telford’s surprise win, where automated software, known as bots, repeatedly vote for a candidate.

Group sabotage or people manually voting for Telford by refreshing their browsers have also been suggested as possible reasons for the unexpected result.

When the shortlist was announced by RBS the prospect of a woman on a Scottish banknote was greeted with enthusiasm.

Alice Prochaska, the principal of the Oxford college which bears Somerville’s name, backed the eminent mathematician and said she was “just about the most influential writer on science of the 19th century”.

“She had really a profound public influence in the 19th century. She deserves far greater recognition than she’s had for the last 100 years or more and I think it’s about time,” she said.

RBS said 400 people suggested 128 figures who could have featured on the bank's new polymer £10 note, which was then whittled down to a shortlist of three for the public to vote on.