The United Kingdom government has fallen well short of the number of ventilators it planned to immediately add to the nation's stocks to treat novel coronavirus patients.

A plan to buy thousands of medical ventilators from a group including the Renault and Red Bull Formula One teams has been cancelled.

The government has confirmed it no longer wants the units because the treatment of COVID-19 patients in hospitals is more complex than anticipated.

The UK's National Health Service needs to increase its stock of ventilators from 10,000 to at least 18,000 and the government has scrambled to acquire enough in time for a peak of cases expected by the end of the month.

Health Secretary Matt Hancock had set a target of increasing the number of ventilators by 1,500 in a week but Downing Street revealed that only an extra 200 have been delivered.

The additional machines, which provide oxygen for people suffering lung failure in severe COVID-19 cases, have been sent out to the NHS in the past week, a spokesperson for Prime Minister Boris Johnson said on Monday.

On April 5, Hancock said the UK had between 9,000 and 10,000 ventilators, with an extra 2,000 spare attached to critical care beds, but he had set a target of 18,000.

Challenged on the BBC's Andrew Marr Show to say how many more ventilators would be rolled out in the following week, he said "there should be another 1,500".

Just more than a week later, the prime minister's spokesman confirmed only 200 extra machines have been added to the total stocks, around 13 percent of Hancock's target.

Lots of countries are trying to source the machines, making it difficult for governments to buy them up. Red Bull and Renault have collaborated alongside Essex-based specialists Lifeline Technologies to produce the BlueSky machine, a ventilator formerly known as Remora, according to The Guardian.

The paper reported that while the BlueSky machine was capable of ventilating patients, clinicians on the government's technical design authority and the Medicines and Healthcare products Regulatory Agency, or MHRA, found it was not suited for treating COVID-19.

A Cabinet Office spokesperson said: "There are another 2,000 mechanical ventilators on order plus thousands of provisional orders for industry-designed ventilators.

"The key point here is obviously the NHS continues to have spare capacity in terms of beds in intensive care units and ventilators, and that anybody who needs intensive care treatment or a ventilator has access to it."

Meanwhile, the government is also set to fall short of its target for COVID-19 tests, with just 18,000 being carried out each day－7,000 short of the 25,000 daily tests by April 18 promised by Johnson earlier.