Flyhalf Cipriani, wing Ashton and centre Luther Burrell were the most high-profile omissions by England coach Eddie Jones as the Australian named a 45-man training squad.
Wasps back row Hughes and Leicester's Zimbabwe-born lock Williams have been given their first chance to impress Jones ahead of the internationals against South Africa, Fiji, Argentina and Australia later this year.
Leicester hooker and club captain Tom Youngs, who was a regular under former England boss Stuart Lancaster, returns after previously being overlooked by Jones.
Gloucester wing Jonny May is also back in the squad following his recovery from knee surgery.
Following their series win in South Africa with England Saxons, Dan Robson (Wasps), Mike Haley (Sale) and Charlie Ewels (Bath) will join the camp, as will Joe Marchant (Harlequins) and Will Evans (Leicester), who were part of the England team who won the World Rugby U20 Championship in June.
England will announce their final squad on September 30 ahead of the internationals, which start against South Africa at Twickenham on November 12.
"This camp sets the scene for November. It's important to catch-up with the players prior to the start of the season and continue to put our plans in place," Jones told the English RFU's website.
"We'll use this time to reset and review each player's goals so they're clear on what is expected of them between now and when we meet up again in October.
"It also gives us an opportunity to meet and assess some new players and ensure they are familiar with the England setup.
"The long-term strategy for England is to develop a side who can be the most dominant team in world rugby, so we've chosen a number of new faces to attend this camp on the form they have shown recently or the potential we see in them."
