The leaflet is being circulated in South Belfast

Former finance Minister Máirtín Ó Muilleoir – who until March was responsible for Stormont’s £10 billion annual budget – is distributing a leaflet which is based on sums which are wrong.

Last night Sinn Fein stood over the literature.

The leaflet is part of Sinn Fein’s attempts to persuade nationalist voters in South Belfast that it can unseat the SDLP veteran Alasdair McDonnell without handing the seat to the DUP, which came second in the constituency two years ago.

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In huge lettering on its first page the flyer states: “Since 2005 Sinn Fein’s vote in South Belfast has doubled. The SDLP’s has halved.”

However, a glance at electoral statistics shows that between the 2005 general election and the last general election two years ago Sinn Fein’s vote has indeed soared – up from 2,882 to 5,402.

However, the SDLP vote has not halved. In fact, the 10,339 votes for Dr McDonnell in 2005 had fallen just 7% to 9,560 votes in 2015.

Even comparing the general election result to March’s Assembly result – despite the fact that that election was a multi-seat proportional representation contest – shows that the SDLP vote has not halved, falling by 19% to 8,353.

When asked whether it could explain the claim – or, if it accepts that it is inaccurate, withdraw the leaflet – Sinn Fein stood over its literature, telling the News Letter: “We will not be withdrawing the leaflet.

“The leaflet reflects the changing voting patterns for the two parties in the South Belfast constituency.”

Sinn Fein senator and former lord mayor of Belfast Niall Ó Donnghaile was among those yesterday distributing the leaflets.

As questions were asked of the party on social media, he played down the situation, asking: “What’s all the fuss about?”

It is not the first time that Mr Ó Muilleoir has made an inaccurate claim at election time.

Two years ago, the candidate took the highly unusual step of posting a video online while polling was continuing in which he confidently stated: “You will have heard by now that I am topping the poll in South Belfast.”