The UK is expecting to receive its first shipment of a new coronavirus vaccine next month, a Cabinet minister has confirmed, amid challenges in international supplies.

Culture Secretary Oliver Dowden expressed confidence that the first Moderna jabs are still on course to arrive in April, in what would provide relief for the overall vaccine rollout programme.

He was doubtful, though, over the resumption of non-essential international travel and acknowledged all legal restrictions may not end in June as hoped, after a Government adviser raised concerns about the full relaxation.

Vaccine supplies have been affected by issues in India, where a temporary hold on AstraZeneca exports has been imposed, and there has been trepidation because of a row with the European Union over exports.

However, Mr Dowden insisted the vaccination programme remains “on course” to hit the target of offering a jab to all adults by July.

“We expect that in April Moderna will come,” he told The Andrew Marr Show on BBC One.

With 17 million doses ordered by the Government, the US vaccine has been approved for use in the UK and would be the third to be rolled out after the Oxford/AstraZeneca and Pfizer jabs.

Professor Adam Finn, an adviser on the Joint Committee on Vaccination and Immunisation, said the limited Moderna stocks will not be a “game changer” because the “small outfit” is focusing supplies on the US.

But, speaking to the PA news agency, he added: “It adds an extra string to our bow, if you like, and it gives us an extra line of security.”

The development came as official figures showed more than 30 million people in the UK have received a first vaccine dose, accounting for about 57% of all adults.

Mr Dowden guaranteed everyone will get a second dose of a coronavirus vaccine within 12 weeks of their first after doubts were raised by French foreign minister Jean-Yves Le Drian.

“Yes, of course, we’ve been planning that all the way through. It’s one of the most important considerations as we’ve rolled out the vaccine,” the minister told Sky’s Sophy Ridge on Sunday.

He said that “we clearly don’t currently have a surplus of vaccines” when asked about suggestions the UK was planning to offer 3.7 million jabs to Ireland.

Charities including Save the Children UK and Wellcome, led by Sage scientist Sir Jeremy Farrar, were calling on Boris Johnson to immediately begin donating vaccines to poorer nations.

With more than half of adults having received a jab, they say the UK is “one of the world’s highest per-capita buyers” of vaccines and is on track to have more than 100 million surplus doses.

“There is therefore the high risk that the UK will be hoarding limited supply whilst health workers and the most vulnerable in low and middle-income countries do not have access,” their letter to the Prime Minister says.

Professor Mark Woolhouse, who advises the Government on the Scientific Pandemic Influenza Group on Modelling (Spi-M), said he was “a little bit nervous about a full relaxation” planned for June 21.

He told the BBC the road map to easing restrictions in England must be “guided by the data” particularly on vaccines, adding: “The idea that we can suddenly emerge from this in one great bound, I think, is a little over-optimistic.”

Mr Dowden said another lockdown “is the last thing in the world we would want to do” but acknowledged dates in the road map may slip if things worsen.

“Of course they could be delayed if the situation deteriorates but at the moment we’re on track,” he told Marr.

Travel abroad is currently illegal other than for a few reasons but a Government taskforce will on April 12 detail a review on whether foreign holidays can return.

Mr Dowden said “all options” are being considered when asked about a possible system that could allow shorter quarantine periods with greater testing for countries deemed less risky.

But he told Ridge there are “challenges around international travel”, pointing towards rising infection rates in Europe.

Meanwhile, the public were warned not to “squander the gains” made in the pandemic ahead of a major easing of the lockdown to allow greater freedoms outside.

Groups of up to six, or two households, will be able to socialise in parks and gardens once more and outdoor sports facilities will reopen as the stay-at-home order ends in England on Monday.

NHS England national medical director Professor Stephen Powis said Covid-19 still has the capacity to “wreak more havoc and ill health on a significant scale”, citing concerns over new variants.

“We’ve made enormous progress that we need to build on and not squander the gains we’ve made,” Prof Powis wrote in the Sunday Telegraph.

“We need to hold our nerve and drive for the line, so everyone can get back safely and soon to our normal lives.”

A further 58 people had died within 28 days of a positive test for Covid-19 as of Saturday, bringing the official UK total to 126,573.

But an analysis of further data, by the PA news agency, shows the wider death toll stands at more than 150,000.

In Wales, lockdown restrictions were eased when the “stay local” requirement was dropped on Saturday and people were allowed to stay in self-contained holiday accommodation.