The Liberal Democrats have defended themselves against accusations they are distributing “misleading and irresponsible” election leaflets that misrepresent newspaper reports as endorsements of the party.

In one leaflet delivered to households in London, a partial headline about the party’s success in a byelection in Wales is attributed to the Guardian when the original author of the words was its own leader, Jo Swinson.

The article attributed the quote to Swinson in the headline reporting that she had declared the party “on the up” after reducing Boris Johnson’s majority to one by snatching the Brecon and Radnorshire seat off the Conservatives in a vote in August.

Heather Stewart (@GuardianHeather) Dodgy leaflet watch: get home to find this from the LibDems, complete with upbeat headline from the Guardian.

Well, it is from the Guardian - but we were quoting Jo Swinson. pic.twitter.com/Ms9Wmd5L2T

In another leaflet handed out in Edinburgh on Wednesday, the party attributes words written by the polling guru John Curtice to the Independent.

Facebook Twitter Pinterest Lib Dem leaflet handed out in Edinburgh. Photograph: SNP Leaflet in Scotland, 6 November 2019

One of its recipients also questioned why the bar chart was not sourced. “There are no labels on the axes, is it votes or number of MEPs? Labour has an arrow pointing down, which is true – the party lost two MEPs and lost votes,” said the Edinburgh voter who passed the leaflet to the Guardian.

“The Conservative arrow points down – it retained its one MEP but did lose votes. Lib Dem points up, it gained an MEP and now has one, the same as the Conservatives, and its vote increased. The SNP has no arrow, yet it gained an MEP to three and its vote increased.”

The voter also pointed out that the Brexit party was not shown. It gained one MEP from having none and its vote was higher than Swinson’s party in the June election, totalling 233,006 votes compared with the Lib Dems’ 218,285.

A spokesperson for the factchecking charity Full Fact said: “Parties and candidates should not be misrepresenting the work of independent journalists in this way. These tactics are misleading and irresponsible.

“Voters will make an important choice about the future of this country in five weeks’ time. Everyone deserves clear and accurate information from campaigns so they can make their own minds up about who to vote for.”

A Lib Dem spokesman said: “Liberal Democrats always provide sources for the data or quotations that appear in local and national election literature … the quote used on our leaflet which was taken from the Guardian, the content of which is entirely accurate, and was within the context of our victory in the Brecon and Radnorshire byelection.”

He said it was “absurd” to suggest that because it did not cite the original source of the quote, its own leader, that it was trying to mislead voters.

“Bar charts reflect a wide range of polling scenarios, in large part dependent on local context. The source of the data will always be made clear on any election literature published by the Liberal Democrats,” the spokesman added.

The Lib Dems have also been criticised for using election material citing data from Flavible, an obscure company which is not a member of the British Polling Council and which has been criticised for using national polls and localising them to project the voting intention for certain constituencies.

The party spokesman said: “Flavible projections are not used on national campaigns. Every time Flavible projections have been used by local campaigns, the source of the data must be clear.”

The Guardian will be factchecking claims made by all parties in the election. If you spot any election material that you think should be factchecked, contact lisa.ocarroll@theguardian.com