"On a scale of one to five, with five best and one worst, where are most councils on their digital journey I'd put about five percent at four to five, 10 percent at four, most at two to three and 25 percent on one," Greenwood told ComputerworldUK.
Greenwood warned "there is no magic bullet" for improving councils' use of digital tools but said a lack of skills, resources and capability is one of the main restricting factors.
"There is a real shortage of resources and skills. Many councils are doing stuff on a wing and a prayer. Often there isn't a web team, there's just one person," he said.
Greenwood suggested leadership, culture and a focus on customers are also key to success for councils.
"It's not normally the tech that's the problem here. It's mindset. It's understanding processes, rethinking the way we do things...you need a real empathy and an understanding of what customers need," he said.
"Every council should be going digital wherever possible as it's a way to be efficient, protect the quality of services or even make them better. They can't afford to be behind the curve, it means cutbacks hit core services, which is unnecessary," Greenwood added.
He acknowledged the difficulty local authorities face coping with ongoing budget cuts but said using modern digital tools offers a way to save money, reduce demand and improve satisfaction.
"There are going to be crisis points from now until basically forever. Rather than reacting to those crises, you want to get to a situation where you're in front and can prevent them."
Socitm identified a "real dip in performance" in user satisfaction in its annual satisfaction survey of local authorities' websites last year, he said.
"We've seen some improvement since, but only back to the levels recorded two years ago," he added.
Greenwood attributed the drop to councils struggling to adapt to a shift to the majority of people using mobile devices to browse online.
Speaking to delegates at Civica Expo, he advised: "Don't waste your time with apps. It's much more important to get your website right for mobile devices first."
However Greenwood dismissed the idea of a single website for local government, describing as a 'total and utter nonsense'.
He said: "A Government Digital Service style mandate wouldn't work in local government. It's a total non-starter. It would take five years just to figure out what it looked like.
"But there's lots of potential for sharing applications and so on. You could develop an organisation councils respected to facilitate sharing and encourage people to do the right things...that would be difficult to set up though, everyone has different priorities."
Greenwood pointed to Croydon Council and East Riding of Yorkshire Council as examples of best practice in local government, saying they had both managed to improve digital customer experience and move more people towards handling their own queries online.
He emphasised the importance of councils needing to get a grip on their data, saying it had been crucial to East Riding's success.
"You can't be successful unless you've got a real handle on the data. Unless you've got the figures to see what you did this year versus last year, you're lost."