The controversial bar charts deployed by Liberal Democrats in election campaign materials can be inaccurate, a senior MP has admitted.

Former maths teacher Layla Moran said the party needed to be “careful” about its use of graphs which appear to show Lib Dems to be the main challengers in a two-horse race with sitting Conservative or Labour MPs.

The party was last week embroiled in a row over a graphic released on social media by its branch in Jacob Rees-Mogg’s North-East Somerset, which put Tories on 38 per cent to Lib Dems’ 32 per cent and Labour on 8 per cent.

But the small print beneath the graph showed that the figures were from a poll of local residents asked which party they would back if they knew Tories and Lib Dems were neck-and-neck, with other parties trailing far behind.

In the 2017 general election, the actual share of votes was Conservative 53.6 per cent, Labour 34.7 per cent and Lib Dem 8.3 per cent.

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Party leader Jo Swinson defended the party’s material when challenged over the chart in a TV interview on Sunday, telling Sky News’s Sophy Ridge: “It was a specific poll in that particular seat and we labelled what the question was. Liberal Democrats have been making progress and winning in that area.”

But asked on BBC Radio 4’s Today programme whether it was “not accurate” for Lib Dems effectively remove Labour from a poll and make it look like a race between them and the Tories, Ms Moran replied: “I agree, and actually I think people need to look very carefully at their bar charts.

“We need to make sure we are representing things well.”

Ms Moran said: “People do need to be careful about the bar charts. I used to be a maths teacher and I insist that we measure with rulers when we put bar charts out and that you are very clear and transparent at the questions you are asking.”

However, she added: “That doesn’t detract from the fact that we are competitive in reality, with votes coming not just from Remainers from the Labour side but also Remainers from the Conservative side.”

Ms Moran said that there had been “huge shifts” in political allegiances over the two and a half years since the 2017 election, with Lib Dems outpolling both Labour and Conservatives for the first time in 100 years in the European elections.

She said Ms Swinson should “absolutely” be invited to take on Boris Johnson and Jeremy Corbyn in election TV debates, which would otherwise have no representative from Remain-backing parties.

Ms Moran confirmed that conversations were under way between Remain-supporting parties including the Lib Dems, Plaid Cymru and Greens over a possible election alliance which might see the parties stand down candidates to help the others in key seats, with an announcement expected “soon”.