Cabinet office minister Michael Gove told a press conference on Tuesday that the "first of thousands" of new devices manufactured in the UK would be sent to the front line next week but he did not specify how many would be in the first delivery.
Officials admitted on Wednesday that the first batch will only include 30 ventilators, with hundreds more expected in the coming weeks.
The NHS currently has around 8,000 ventilators to treat coronavirus patients but another 30,000 devices will be needed to cope with the expected peak of the outbreak in April.
Downing Street said 30 new ventilator devices would be delivered to the NHS next week from Oxfordshire-based firm Penlon, as part of a consortium including Ford, Siemens, Mercedes, McLaren and Meggitt.
"As Michael Gove set out last night, we would hope to see the first ventilators from this batch being delivered to the NHS next week," the prime minister's official spokesman said.
"I think we expect that first batch to be up to 30 ventilators, with hundreds more from that particular consortium to follow in the coming weeks.
"That's just one of the consortiums that we've partnered (with) - there are thousands more ventilators in the pipeline from other manufacturers and suppliers who are rapidly working on new devices."
The Treasury also announced plans to waive import taxes on ventilators and other vital medical equipment from outside the EU, to speed up orders of 8,000 devices from abroad.
Engineering firm Dyson has also taken orders from the government for 10,000 of its prototype ventilator, which is awaiting approval from the regulator.
Separately, 10,000 new oxygen machines – known as CPAP (continuous positive airway pressure) devices – are also being produced to help patients struck down by the virus.
However the government has faced criticism for failure to act sooner on supplies of ventilators and other vital medical kit.
Former Tory justice minister Dr Phillip Lee, who resigned to join the Liberal Democrats, said ministers knew in January that there was a "ventilator capacity problem" and that Covid-19 caused significant respiratory problems.
He told Sky News: "I don't quite understand how the government didn't at that point err on the side of caution and go, 'okay we need to start rolling on ordering ventilators'.
"There's a strong argument that we should have a batch of ventilators, 20,000 or 30,000, sat in a warehouse somewhere off the back of the exercise in 2016.
"Even if we had'nt done that, we could at least have pressed the button on ventilator capacity and I would also argue testing capacity in January, as opposed to what actually happened where we had a panicked plea from the health secretary to produce ventilators six weeks after the first Covid-19 case in the UK."