Around two million Universal Credit claimants are to have their benefits investigated by the Department for Work and Pensions (DWP).
The Targeted Case Review initiative will check if claimants are legitimately entitled to their payments and whether they are on the right amount.
The review was announced last year by the DWP as part of the Government's plan to tackle fraud in the benefit system.
The update came after the Shadow Secretary of State for Work and Pensions Jonathan Ashworth asked the DWP what steps it was taking to reduce benefit underpayments due to official error recently.
In a written reply, the DWP's minister of state for disabled people, health and work said the Government department was "committed to identifying errors and rectifying them as quickly as possible".
He wrote: "The Government is fully committed to ensuring that historical errors made by successive governments are addressed as quickly as possible and where these are identified, ensure that appropriate action is taken to rectify the claim."
The minister then explained the ongoing review of Universal Credit confirming that two million existing Universal Credit cases would be looked at in the next five years.
He said: "The department's Quality Framework means we constantly check the accuracy of agents' work, which helps identify any additional training requirements. It also means we can update training material and instructions as required.
"Alongside the department’s quality checking regime, our Targeted Case Review initiative will review two million UC (Universal Credit) cases over the next five years, checking entitlement and helping ensure people are receiving the right amount of benefit."
In July 2022, it was revealed that the DWP had given Universal Credit to 125,000 people who shouldn't have been eligible during the Covid-19 pandemic.
The mistaken payments were blamed on the DWP having paused its usual face-to-face identity verification for Universal Credit claimants at the start of the pandemic.
Several thousand were also told to pay back the cash.
As part of its Fighting Fraud in the Welfare System plan, the DWP said it was to create a new team of 2,000 staff to review the claims.
The latest figures show around 5.8 million people across the UK currently receive Universal Credit from the DWP.
The plan means around a third of these existing claims could be investigated by the DWP.
