One constituent took to social media to warn others about the letter from Sarah Atherton, the MP for the North Wales constituency, which she had to pay to collect.

The constituent, who wished to remain anonymous, received a note from Royal Mail, telling her they had a letter for her to collect from the sorting office.

She could not tell from the note what the letter was or who it was from.

She said that she had "wasted time and effort" as well as having to pay a £2.50 fee to collect it from the sorting office.

"People haven't got money to waste on things like this, especially when there's a cost of living crisis at the moment," she told Sky News.

The mother of two said that 48 hours after she complained to Ms Atherton's office, she is yet to receive an offer of reimbursement.

The Wrexham constituent added that Royal Mail had a "considerable amount" of the leaflets at their sorting office for the area.

'We apologise'

Sarah Atherton said in a statement: "Over 1000 surveys were posted and only a handful of people have been in contact to explain they had to pay postage. We apologise for the inconvenience caused.

"We are looking into what went wrong so this doesn't happen again. If those who have been charged want to email This email address is being protected from spambots. You need JavaScript enabled to view it. with proof, we will reimburse the cost.

"People want to make this stamp story a political one to take away from the message that we need to concentrate on better access to healthcare in Wrexham.

"My campaign to improve our health service continues, so please let me know your experiences by completing the survey and returning it in the pre-paid envelope provided."

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Royal Mail said in a statement that charges are usually applied when "a customer has inadvertently posted items with insufficient postage or invalid stamps".

They advise customers who are suspicious of any stamps they have been sold to report it to them, adding that stamps are available to purchase "in Post Office branches throughout the UK".

"We recommend customers always buy stamps from reputable Royal Mail approved outlets," the statement added.