The Government’s employee furlough scheme has received 17,500 applications an hour since it was launched Monday morning, according to Chancellor Rishi Sunak.

At the daily Government briefing, the Chancellor said 140,000 firms had applied for the cash under the coronavirus job retention scheme between 8am and 4pm.

He added that around one million workers are expected to benefit from the scheme, which guarantees 80% of wages up to £2,500 per employee.

A report by the Resolution Foundation estimates the total cost of the opening day’s applications alone will be at least £4.2 billion over three months.

The scheme had initially seen employers claim for 67,000 jobs in the first 30 minutes, according to HM Revenue & Customs (HMRC).

Early indications from businesses trying to access the scheme are that the online portal continues to hold up well – with officials saying the newly-built systems can hold up to 450,000 applications an hour.

The Federation of Small Business (FSB) national chairman, Mike Cherry, said: “Initial feedback about the job retention scheme has been positive… The real mark of success for this scheme will be money in employer back accounts by the end of the month.”

Businesses have until Wednesday to apply, with Mr Sunak revealing payments will be made within six working days from applications being received.

He said: Over 140,000 firms have applied and the grants they’ll receive will help pay the wages of more than a million people… who, if they hadn’t been furloughed, would have been at risk of losing their job.

“Firms applying today should receive their cash in six working days and HMRC will continue to provide updates on the number of people furloughed.”

The launch of the scheme comes as the Government was warned of the economic cost for many companies of any delay in its implementation.

Mr Sunak added: “Our unprecedented job retention scheme will protect millions of jobs across the country and is now up and running.

“It’s vital that our economy gets up and running again as soon as it’s safe – and this scheme will allow that to happen.”

The sheer scale of applications for the Government’s Job Retention Scheme on its opening day shows just how badly the scheme is needed

Approximately 5,000 HMRC staff are operating the scheme, intended to assist thousands of UK firms, a statement from the Treasury said.

Phone lines and web-chat services will be available to help answer applicants’ questions, with the scheme launching 10 days ahead of schedule, it added.

The Chancellor earlier announced the scheme will be extended for a further month until the end of June, in light of the ongoing countrywide Covid-19 lockdown.

Dan Tomlinson, an economist at the Resolution Foundation, said £4.2 billion could be claimed on Monday alone.

He added: “The sheer scale of applications for the Government’s Job Retention Scheme on its opening day shows just how badly the scheme is needed.

“The next challenge is to make sure the payments to firms get made as swiftly as possible, as the scheme is very much on the front line of protecting both firms and family incomes amid a huge economic crisis.”

With April’s payday approaching, it is essential that the application process is smooth and that payments are made as soon as possible

Adam Marshall, director general at the British Chambers of Commerce (BCC), said: “Our research indicates that two-thirds of firms have furloughed some portion of their workforce.

“With April’s payday approaching, it is essential that the application process is smooth and that payments are made as soon as possible. Any delay would exacerbate the cash crisis many companies are facing and could threaten jobs and businesses.”

Jim Harra, chief executive of HMRC, said he was “very confident” the system would work after it had been “tested at volume”.

Speaking to BBC Breakfast, he said: “Of course, there is a limit to the capacity of the system, so if every employer tries to use it at 8 o’clock this morning some will be asked to queue or come back later, that doesn’t mean the system has crashed, it simply means that it’s full.

“But employers can claim any time over the few days, between now and Wednesday, and we will have the money in their bank account by April 30.”

He added: “So I’m confident that if employers are patient, use the system, it’s available 24/7, and as I say, if your payroll date is April 30 you can claim any time today, tomorrow or Wednesday and we will get that money into your account.”