Test vice-captain Stokes was arrested last month on suspicion of causing actual bodily harm and suspended, along with Alex Hales, from internationals until further notice following an apparent fight outside a nightclub.
He was included in the Ashes squad despite reportedly injuring his hand in the incident that led to his arrest.
The 26-year-old Durham all-rounder was released without charge but remains under investigation.
The ECB also announced that Middlesex paceman Steven Finn will be added to the Ashes touring squad in light of the ongoing police investigation.
"With the Ashes just around the corner, it's important to give the players, the coaching staff and supporters some clarity around a complex situation," said director of England Cricket Andrew Strauss.
"This decision will help us in the weeks ahead and give every player and the whole England set-up the best chance to focus on the challenge ahead in Australia.
"Steven is a high-quality cricketer, with considerable experience of both international cricket and Australian conditions. The selectors believe he will add to the range of options and the squad will be further supported by the arrival of the Lions in Australia in November."
"We have spoken to Ben and assured him that our decision in no way prejudges the outcome of the ongoing police investigation or cricket discipline commission process, as can be seen by the award of central contracts," Strauss added.
The board confirmed the awarding of central contracts for Test and limited-overs cricket, with Stokes handed contracts for both. Hales has been retained as a limited-overs specialist.
In a separate matter, the ECB has also fined and issued a formal written warning to Jonny Bairstow, Jake Ball and Liam Plunkett following a disciplinary investigation into behaviour during the recent one-day series against the West Indies.
No further details have been given but the ECB has stated clearly that this issue is "unrelated to the investigations into Ben Stokes and Alex Hales".