A letter, signed by individuals at 14 organisations has been sent to the Government Digital Service, calling for improvements to the project, which was introduced two years ago to simplify digital procurement for public sector bodies in the UK.

The letter voices concerns over the level of understanding on how to use the CloudStore and says that some purchasing bodies could face legal challenges because they have deviated from the G-Cloud buying guide.

The letter says: “As opportunities through the framework become larger (and more valuable to suppliers), there is an increased risk of challenge from those suppliers who are losing revenues to G-Cloud.

“A successful challenge could potentially damage the integrity of the initiative, and all that it promises to deliver to the UK public sector.”

The authors recommend that a system is established to enable suppliers to report variances from the guide to the G-Cloud team and the Crown Commercial Service.

One of the signatories to the letter, Mark Webber, partner at law firm Osborne Clark, said: “In order for G-Cloud to continue in the right direction, clear guidance around interpretation of contract terms to enable safe contracting is essential to ensure that all purchasers and providers are able to make the most of the opportunities available."

The letter says that the next iteration of the project, G-Cloud 5, should incorporate a template collaboration agreement, to avoid uncertainty over whether suppliers are allowed to do so.

It also calls for a review of the standardised contracts which are available under the scheme.

“Contractual standardisation generates challenges: for the buyer whose default is their own terms and conditions; and for suppliers whose own terms and conditions are at the bottom of a contractual hierarchy,” it said.

It said that some buyers avoided G-Cloud because they did not believe the terms were sufficiently robust.

Among other suggested improvements, the authors say that the maximum contract term should be increased from two to three years, to encourage take-up.

They also called for clear guidance to be quickly produced over how the new Government Security Classification Policy, GPMS will relate to G-Cloud.

Their letter also calls for the removal of many of the 13,000 services currently available on the store because they are out of date.

It said: “It is doubtful that all or even many of the lot one, two and three services available meet the National Institute of Standards and Technology definition for cloud services – or that they demonstrate the essential characteristics required by the G-Cloud 4 procurement, namely truly on demand, measured service.”

As well as a number of suppliers and IT law firms, the letter was signed by Andrew Curtois, senior IT category manager at Westminster City Council.

A Cabinet Office spokesperson said: "Much remains to be done to embed G-Cloud so that organisations across the public sector – and ultimately the taxpayer – benefit from access to the most innovative, cost-effective solutions offered by the widest range of suppliers.

“We are always looking for feedback from suppliers and customers, both positive and negative, and we continue to make improvements to G-Cloud and CloudStore with each new iteration of the framework.”