The Royal Free Hospital in Hampstead

NHS workers were invited to sign-up for a “pay as you earn” payroll system at the Royal Free Hospital – a service provided by the collapsed company at the centre of a lobbying investigation.

Former prime minister David Cameron has been asked to explain his work for Greensill Capital, which he joined as a paid adviser in 2018, after it was revealed he organised a “private drink” between health secretary Matt Hancock and the company’s chief executive and sent text messages to Chancellor Rishi Sunak.

Months later, a rollout of Earnd, an app which allows staff to draw down their pay day by day, began in the NHS with the Royal Free being the first hospital to take part.

Former Prime Minister David Cameron

Earnd had previously been acquired by Greensill last March.

In promotional material put out by NHS Providers, a staff member at the Hampstead hospital is quoted: “I’m doing a worldwide recruitment drive at the moment, and I’ve put it [Earnd] in there as one of the main benefits of working for the Royal Free.”

NHS hospitals were facing a critical recruitment challenge during the first wave of the pandemic with so many staff sick themselves or quitting because of safety fears.

Announcing its new service, Earnd had said: “NHS trusts can use Earnd to incentivise more doctors, nurses and other healthcare professionals to join their ‘bank’.”

However, after Greensill went into administration the payroll system was scrapped and the Royal Free no longer has a deal with the firm. A Royal Free spokeswoman said the trust would not comment.

Mr Cameron broke his silence this week to say he should have used “only formal channels”.

The government, however, has ordered an independent investigation to examine the firm’s role and the communications that took place.

Prime minister Boris Johnson said he shared concerns about “the stuff we’re reading at the moment.”