A developer behind the new NHS Scotland Covid vaccine passport app says he is “confident” it can withstand high levels of user demand after being “robustly tested”, despite a barrage of major problems being reported on social media just hours after its launch.

Scots are now able to access their vaccines certificates – an NHS first – to provide digital proof that they have had two doses of the vaccine in order to enter certain night time venues and large outdoor events such as music festivals.

The Covid Status app was made available to download at 17:30 yesterday in preparation for the new scheme.

But reports on social media suggest that serious issues have arisen with users unable to verify their identities, especially when entering their NHS Community Health Index (CHI) number – a unique 10-digit code which is allocated to every patient on first registration with the service.

Some have also struggled to log in, whilst others have expressed concern that those without a passport or driving license are unable to use the app.

The Scottish government said the volume of people trying to access the app may be responsible for the issues.

Steven Flockhart, director of cloud engineering and digital operations at NHS National Services Scotland Digital and Security, played a key role in the creation of the platform.

As the app went live, he said: “We have tested demand successfully based on the volume of PDF download requests when the QR code was first launched, so we are confident this can be supported by the service upon launch.

“The app has been robustly tested and will deliver a secure digital solution for citizens to provide proof of vaccination where required.”

He added: “Delivering an app which meets the needs for a secure, digital solution in a very short delivery timeline has meant that we have taken every care and precaution to get this right on behalf of the citizens of Scotland.”

However one woman described the app as “abysmally designed”. She tweeted: “In all seriousness, was this app ever tested at all? Because it doesn’t function with screenreaders, isn’t compliant with WCAG [Web Content Accessibility Guidelines] 2.1 AA, the forms are abysmally designed, the emails from Microsoft make it look like a proof of concept, and it doesn’t even work.”

Sandy Mathers said: “It won’t believe I exist even with my CHI number. That’s on the one occasion the face recognition actually worked. This is very disappointing. It tells me to contact the help team. There is no link to do so.”

Professor Bill Buchanan OBE, one of the UK’s leading cryptographers, was also among those who expressed disappointment at the Covid status app rollout.

He said he had tried to verify his ID on the system but that scanning his driving licence did not work, and even though his CHI number pre-populated his data, the platform failed to match his records.

He said: “This was our big chance in Scotland to show that we really are a digitally focused country and to build a trusted identity infrastructure for the future. We have lots of great digitally-focused people that could have helped with this.

“But the whole system currently lacks feedback and lacks integration with other systems. It looks like a generic system that has been shoe-horned in for this application, and perhaps not really tested at scale. It also has US spelling, which shows a lack of customisation for the local market.”

He said the verification code part of the system was “confusing” and that he found the lack of integration with digital identity platform Yoti “surprising”. He pointed to “deeper” longer-term issues with identity-based projects in government which often “shoe-horn the citizen into existing systems”.

He added that the whole infrastructure needs to be “redesigned” and privacy and protection of data made paramount.

At a political level, he believes there needs to be greater clarity of vision and leadership for where Scotland is going in terms of its future data architecture, and that the citizen should be at the heart of this.

And our editor Kevin O’Sullivan, who attempted to use the app this morning, faced a similar problem.

After downloading and installing the app, his details were not recognised in the verification process.

After uploading a picture of his passport and one of his face to ensure the two matched, he entered his CHI number – only to be told ‘No Match Found’.

He said: “I tried repeatedly and did things like varying the postcode – space between third and fourth character and no space – but that had no effect. It pre-populated my middle name and surname correctly on the ‘confirm’ page but it didn’t have an apostrophe in my surname, so I am wondering whether that might be an issue in the database?”

Likewise, business owners, who are expected to implement the new software from today, have raised concerns.

The Scottish Hospitality Group posted a screenshot of the Covid Status app on Twitter, which reads ‘Something went wrong. We’re working on it’, accompanied by the tweet: “How are businesses affected by this from 5am tomorrow supposed to deal with things like this?

“We said all along, unworkable and rushed. This wasn’t about business not being ready, it was about NOBODY being ready, but politicly it was better to say time was given to businesses.”

The Scottish Conservatives are now calling on the government to “indefinitely” delay the introduction of the vaccine passport scheme and “prevent a weekend of chaos”.

A Scottish Government spokesperson said: “Some people may be experiencing issues which are likely to be caused by extremely high initial traffic and a large number of users trying to access the app at once. We advise people whose data is not found to try again a couple of hours later.”

Douglas Ross, leader of the Scottish Conservatives, said the Covid passport plan should be “scrapped altogether”.

He added: “The SNP Government has just a few hours to act quickly and prevent a weekend of chaos at venues across Scotland. Thousands of people will be at the football and going out to hospitality premises this weekend. At an incredibly challenging time, businesses will lose out if this app is still not working.

“The SNP must order an emergency stop to this policy now, before it hurts businesses and jobs. So far, they have arrogantly ploughed on regardless, against warning after warning from the opposition and business.”

Alex Cole-Hamilton, leader of the Scottish Liberal Democrats, said the public’s confidence in Covid ID cards has “crumbled”.

He said: “The Information Commissioner’s Office says trust is both necessary and key to the success of this scheme. What little confidence existed crumbled last night. The launch was shambolic. Thousands of attempts to access Covid ID cards hit the buffers.

“I warned that the IT wouldn’t be ready or up to the job when the first minister first unveiled this SNP/Green assault on medical privacy. The government has had a litany of tech problems during and before this crisis. Once again it can’t even get the basics right. The Information Commissioner should intervene to stop this scheme now.”

Jackie Baillie, the deputy leader of Scottish Labour, said the launch of the app had been a “complete shambles”.

She added: “I have already been contacted by several constituents complaining that the app crashed on them. It is typical of the SNP to rush this out when it clearly doesn’t work. This is embarrassing for the Scottish government. They need to get a grip and fix the app urgently.”

It was confirmed that the Covid vaccine certification scheme would be introduced on 1 October by SNP ministers on Tuesday 28 September.

However, measures will not be legally enforced until 18 October, giving businesses a 17-day “grace period” to test and adapt to the new system.

When confirming the scheme would go ahead earlier this week, John Swinney, deputy first minister and secretary for Covid recovery, said: “This is a very limited scheme and we hope this will allow businesses to remain open and prevent any further restrictions as we head into autumn and winter.

“We know from expert public health analysis that we must do all we can to stem the rise in cases and reduce the pressure on the NHS. Vaccine certificates have a role to play as part of a wider package of measures. They add a further layer of protection in certain higher risk settings.

“I also want to ensure that as many people get vaccinated as possible and particularly to increase uptake in the younger age cohort, so anything that helps to incentivise that is helpful.”