Downing Street has moved to play down fears over missing postal ballots, saying they disagreed with John Swinney’s claim that voters were being disenfranchised.

However, one leading Scottish Conservative candidate said he feared the growing crisis could stop him from winning on Thursday.

It is not known how many people have been affected, but most of those reporting difficulties applied for a postal vote after June 7 but ahead of the June 19 deadline.

While it is a problem across the UK, it is being keenly felt north of the border where most schools are now closed for the summer, and many families are heading off on holiday.

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Hundreds of voters across the country have now appealed to councils for emergency replacement postal votes ahead of the election.

Aberdeen told The Herald they had issued 148 replacement postal votes by Monday morning, while Glasgow had issued 170 by Friday night.

East Lothian sent out 44 replacements, while Midlothian issued 27.

Although these are relatively small numbers, they could make all the difference in close contests.

Last week, a Survation poll for The Herald and Ballot Box Scotland suggested around 15 of Scotland’s 57 constituencies were on a knife edge, where the result could go either way with a swing of 2% or less.

The First Minister has previously said he is “worried people will be disenfranchised.”

On Monday, when asked if the Prime Minister shared Mr Swinney’s concerns, Mr Sunak’s official spokesman told reporters: “No.

“We are aware of some concerns around the printing and delivery of postal ballot packs in some local areas.

“We’re working closely with the Electoral Commission, returning officers, Royal Mail and the print suppliers to support the resolution of these issues.

“We understand that the Royal Mail will also be conducting sweeps of their delivery system on polling day to make sure that any ballot packs still in the postal system are identified and passed to returning officers ahead of polls closing.

“And anyone who hasn’t received their postal ballot yet may want to contact their returning officer or arrange for it to be reissued, or to arrange for an alternative avenue to cast their ballot.”

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Speaking to The Telegraph, Luke Graham, the Tory candidate in Perth and Kinross-shire, said more than 20 voters had told him they had not received their papers before going on holiday.

In 2017, the SNP won the seat by 21.

Mr Graham said: “It absolutely could be the difference between winning or losing. It impacts all parties but I’ve had at least 20 people contacting me to say they have not had their ballot paper before going away on holiday.”

“It’s incredibly frustrating – nobody should be disenfranchised like this,” he said. “I don’t know whether it’s the Royal Mail or the printing company but there needs to be an investigation and action taken. I want every vote to come through Scottish Labour leader Anas Sarwar has also voiced concerns.

He said: “I’m deeply concerned across the board, because one person disenfranchised is one person too many, regardless of their politics, regardless of who they vote for, because that’s the fundamentals of our democracy.

“And I’m aware of several cases already of people who have left to go on holiday and didn’t receive their postal votes on time. That is not acceptable.”

He also said councils should take a “consistent” approach to setting up the emergency postal vote stations to avoid any confusion.

At the weekend, Mr Swinney said there appeared to have been little consideration given to the issue of Scotland’s summer school holidays in the timing of the election.

Speaking to Sunday Morning With Trevor Phillips on Sky News, Mr Swinney said: “Unfortunately, there is nothing that can be done.

“They have to be here to be able to exercise their postal vote, if it’s been delivered to the house, or if there is an alternative arrangement in place.

“There are no other proxy arrangements that can be put in place, but I think it’s illustrative of the fact there was no thought given to summer school holidays.”

Scottish Tory Charman, Craig Hoy rejected that. He told The Herald: “The election was called five weeks ago, six weeks ago nearly.

“Plenty notice was given. There's no issue about holding an election during a holiday period. It's happened in the past.

“Obviously, we might want to look at this afterwards, but I don't think we should be attributing blame to one set of politicians or to one component part of this process.”

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As spokesperson for the Electoral Commission said: “Tens of thousands of postal votes were delivered over the weekend. We know local authorities and Royal Mail are working to get the final ones out as soon as possible.

“As is the case at all elections, given the electoral timetable, there is a short window of time for administrators to prepare and dispatch postal votes.

“Anyone who hasn’t yet received their postal ballot pack should request a replacement from their local authority. Voters have the option to hand their postal pack to their polling station on polling day if they are concerned about posting it.

“They can also ask someone to hand their ballot pack in on their behalf. Voters can hand in a maximum of five postal ballots in addition to their own, and will be required to complete a form at the polling station when doing so.

“We recognise the pressures on the postal voting system due to the holiday season. We are continuing to provide advice and guidance to electoral services teams to support them with the postal voting process.

“Following the election, we will undertake research with voters and electoral administrators to understand their experiences at this poll. The administration of postal voting is one of the areas we will look at.”