Digidentity joins credit check giant Experian, which has been sole provider to the scheme so far, during a private beta from February to October and the ongoing public beta which launched in October.
Digidentity is an identity management platform currently used to verify Dutch citizens online by government agencies in the Netherlands.
A number of users found themselves cut off from the online Common Agricultural Policy service because they were unable to certify their identity when the public beta launched this autumn.
The Government Digital Service (GDS), which is responsible for GOV.UK Verify, said it made alterations to the service after the issues became apparent.
GDS said it is using the beta phase to "gather feedback from customers and data to make further improvements".
The team have indicated they expect over 400,000 people to be using GOV.UK Verify by March. A number of government services are due to start using the scheme to certify users between now and then.
These include new online services for tax credit renewals, PAYE and self-assessments, viewing your driving licence, making redundancy payments and the government's troubled Universal Credit scheme.
There are a further three firms with IDA contracts signed in September 2013: Mydex, The Post Office and Verizon.
ComputerworldUK understands the Post Office and Verizon are due to join the programme before the end of this year. It is unclear when the final supplier, Mydex, will officially start providing services.
GDS has said it plans to launch a new procurement round to expand the current list of providers, due to kick off with a contract notice in the Official Journal of the European Union by 12 December.
A Labour Party-commissioned report on public sector IT out last month said the GOV.UK Verify scheme is "running significantly behind the initially committed schedule" and may need to be reviewed by the next government if it is not in a more 'stable' position by next May.
Image credit: GOV.UK Verify homepage