Nic Harrison, the head of the troubled Gov.uk Verify identity assurance programme, is leaving his job at the Government Digital Service (GDS) to return to the Department for Work and Pensions (DWP).

Harrison joined GDS on a two-year contract in September 2016 and, as director of service design and assurance for digital identity, has been in charge of Verify during a critical period. He was brought in by GDS director general Kevin Cunnington – also ex-DWP – soon after the latter’s appointment, along with several other executives from Cunnington’s former leadership team.

GDS has not yet announced a replacement, and Harrison’s departure will raise further questions about the future of the Verify programme.

Verify was allocated a significant budget in the 2015 spending review and hailed as a flagship project for GDS. In February 2017, the government transformation strategy committed GDS to delivering to 25 million users of Verify by 2020.

However, currently only 18 digital services use Verify, and only half of all users attempting to create a Verify identity are successful. Less than 2.7 million people have registered with Verify, with about 134,000 new users in July – an adoption rate that would take 14 years to reach the 25 million target. In May, Harrison acknowledged that the numbers “still aren’t stellar”.

He has been leading an effort to review the future of Verify, but GDS has yet to provide details despite widespread calls to clarify the direction of the project.

In June, Computer Weekly revealed that GDS lost control of digital identity policy to the Department for Culture, Media and Sport, although it retained ownership of Verify.

A Cabinet Office spokesperson said: “Nic is returning to the Department of Work and Pension in line with his contract. We would like to thank him for his contribution to GDS over the last couple of years, and look forward to collaborating with him in his new role at DWP. We will announce his replacement in due course.”

Despite attempts to make Verify the identity system for all digital government services, several parts of the public sector are developing their own alternatives. HM Revenue & Customs is working on a new version of its existing Government Gateway, while NHS England is developing its own identity system, after saying Verify is not secure enough for the health service.

The Department for Work and Pensions is using Verify as part of its Universal Credit system, but was forced to develop its own identity system as well, after finding that hundreds of thousands of benefits applicants could be unable to register successfully on Verify.

The Scottish government is also pressing ahead with its own digital identity plans, with the aim of producing a prototype in August 2018.