Royal Mail has hit back at criticism from a Government minister over reports of delays to postal vote delivery, insisting there is “no backlog” ahead of the General Election.

Kevin Hollinrake was said to be “urgently” investigating a failure to get ballot packs to people in some constituencies in time for polling day on Thursday.

He suggested Royal Mail should have anticipated extra demand for postal votes during the summer holidays amid fears some could be left disenfranchised by the issues because they are already overseas.

It’s not acceptable it’s sat in sorting offices. It needs to be delivered to people’s houses. They need to put more people on to do that

But in a statement issued on Tuesday, a spokesperson for the service said: “We have no backlog of postal votes and, whilst we are not complacent, we remain confident that postal votes handed to us on time will be delivered prior to polling day.

“Where specific concerns have been raised, we have investigated and confirmed ballot packs are being delivered as soon as they arrive in our network.

“We would welcome a review into the timetable for future elections with all stakeholders to ensure that the system for printing and administering postal votes before they are handed to Royal Mail works as smoothly as possible.”

Appearing on Tuesday’s morning broadcast round, health minister Maria Caulfield had said that Mr Hollinrake, the postal affairs minister, was “in direct contact” with Royal Mail over the problem.

“Kevin is investigating this urgently,” she said. “I know there’s extra resources going into this to try and do a sweep of all the sorting offices and make sure they’re out there.”

But sources in Royal Mail told the PA news agency later on Tuesday that Mr Hollinrake has not yet raised his concerns with the postal service to date, in apparent contrast to Ms Caulfield’s remarks.

It comes after Mr Hollinrake told the Telegraph that he did not think there was any issue at play “other than Royal Mail being competent and fulfilling their obligations under the USO (Universal Service Obligation)”.

“There’s a resourcing issue. They have recruited extra people and I welcome that but they’ve got to make sure they’ve got the right number of people to deliver the mail at busy times like this,” he told the paper.

“It’s not acceptable it’s sat in sorting offices. It needs to be delivered to people’s houses. So they need to put more people on to do that.”

Scottish First Minister John Swinney warned some Scots could be “disenfranchised” if their postal votes cannot be filled out and returned on time.

Numerous voters north of the border have reported still not having received their ballots, and many have now left for a holiday overseas.

The electoral watchdog has said it recognises the pressures on the postal voting system due to the holiday season and will look into its administration after this election.

Meanwhile, the Local Government Association called for a review of the already “overburdened” system put under extra pressure by an “unprecedented increase” in people voting by post.

On Monday, the Prime Minister’s official spokesman said Rishi Sunak is not concerned that some people could be deprived of a vote as a result when asked by journalists.

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

Mr Swinney rebuked the Prime Minister over the remarks, accusing him of attempting to “dismiss and ignore” the concerns of voters, which he claimed was a “democratic disgrace”.

Sir Keir Starmer and Stephen Flynn also expressed concern over the issues, with the Labour leader calling on Mr Hollinrake to request an emergency meeting with Royal Mail.

Speaking to journalists on the campaign trail on Tuesday, Sir Keir said: “They need to sort it out and get on with sorting it out because what you can’t have is people who are entitled to a vote not being able to exercise it.”

He added: “If the Post Office minister hasn’t met them, do it now in the next hour or two.

“Seriously, we are running out of time, it’s not something we can do tomorrow.”

SNP Westminster leader Mr Flynn, who says he has received numerous emails from voters who have not received their postal ballot in Scotland where school holidays have already begun, questioned Royal Mail’s denial of a backlog.

“I would probably argue some of the Royal Mail sentiments in relation to that because if there’s not a backlog, where’s the postal votes for my constituents, people that I’ve represented and hope to represent again, who don’t have access to the postal votes?” he said.

Polling expert John Curtice suggested the delays would likely hit Tories the hardest, if they had any effect.

“We know that postal voters tend to be somewhat older – older people are somewhat more likely to vote Conservative, so if it is going to have any particular impact then the truth is that probably, question mark, it may at the margin be more likely to which Conservatives will lose out,” he told BBC Radio 4’s World at One programme.

The chief executive of the Electoral Commission suggested the system had struggled in some areas with the turnaround after Mr Sunak called a surprise summer election, but said about 6.7 million postal votes had already been sent.

“That’s better than previous elections,” Vijay Rangarajan said.

“At the moment the printers have been working flat out, Royal Mail have been working really flat out, so have electoral administrators to try to get postal votes out so everyone can vote.”

He said the last batches should have been delivered to people on Monday and Tuesday, but that if voters are already abroad then “there’s very little” that can be done.

The regulator has said that “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”.

Local councils are responsible for sending postal ballot forms to voters.

Completed postal votes must have reached councils by 10pm on polling day.

A Local Government Association spokesperson said: “Councils and electoral staff across the country have been doing their utmost to ensure the smooth running of this election and that people can vote.”

They added: “We are aware of reports of incidents where delays have happened. The postal vote system could benefit from review and more could be done to support Royal Mail and printers to be ready to deliver elections.”