Boris Johnson has suggested the limiting factor in expanding the UK’s coronavirus vaccine rollout is waiting for batches of the jab to be tested.

Ministers have said the NHS has the capacity to deliver two million doses a week of the Oxford vaccine once it receives supplies from the manufacturers.

The Prime Minister said the issue is not supply or staff, but waiting for batch approval.

He explained: “We have the capacity, the issue is to do with supply of the vaccine.

“It’s not so much a manufacturing issue although that’s part of it.

“Each batch needs to be properly approved and quality controlled.”

Mr Johnson said there would be a “massive ramp up” in vaccination numbers.

He added: “There’s a massive ramp up operation now going on.

“The rate limiting factor is now not supply of vaccines, although we want that to go faster, it’s getting them properly tested and getting them to the NHS.

“It’s not the ability to distribute the vaccine, it’s not the shortage of staff.

“It’s getting it properly tested. That will ramp up in the weeks ahead.”

Dr June Raine, chief executive of the Medicines and Healthcare products Regulatory Agency (MHRA) told BBC Radio 5 Live the National Institute for Biological Standards and Control batch release biological medicines as their job.

She added that the process begins before approval is granted, to look at what is needed to do all the right checks and “therefore at the time of approval everything is there and in hand”.

Asked if the MHRA is able to do this as quickly as possible, Dr Raine said: “Yes, and we have scaled up, in the fullness of time, if there are more vaccines, to be able to batch release all of them.

“I was really proud last Wednesday when we approved the AZ vaccine, the Oxford/AZ vaccine that we had approved the first batch the night before. We are that nimble and that quick.”

She added: “The MHRA is fully scaled up to do the batch testing that’s so important for confidence as the new products come through.

“It’s a supply chain that goes right back from the manufacturer, right through to MHRA, and then on to the clinical bedside or where the vaccines are delivered, so we are a step on the road but our capacity is there, I’m very clear about that.”

The Government has secured 100 million doses of the Oxford vaccine, enough for most of the population.

While around 530,000 doses are to be available from Monday, the Department of Health and Social Care (DHSC) said tens of millions more are to be delivered in the coming weeks and months once batches have been quality checked.