The Saracens winger, 28, was cited for making contact with the eyes of Ulster's Luke Marshall in a European Champions Cup game.
The suspension came just a week after he was recalled to the England squad, 18 months after his last appearance.
Ashton pleaded not guilty at a hearing on 20 January and is appealing against the level of the sanction.
He received the full written decision of the independent disciplinary hearing judicial officer on Friday, 22 January.
England begin their Six Nations campaign in Scotland on 6 February and end it on 19 March in France, with Ashton's ban finishing on 28 March.
Head coach Eddie Jones said he would wait for the outcome of any appeal before naming a replacement.
However, Bath wing Semesa Rokoduguni has been called up as cover and the 28-year-old will join up with the England squad until a final decision is made on Ashton's case.

The alleged victim, now in his 40s, was under 16 when he was at Grafton Close Children's Home, during the 1980s.
The man told the jury at Southwark Crown Court how Father Anthony McSweeney performed a sex act on him and then took out a camera.
Fr McSweeney, 68, of Pease Pottage, West Sussex, denies abusing boys at the home in Hounslow, west London.
The priest, of Old Brighton Road North, denies four counts of indecent assault, three counts of making indecent images of a child and one of taking indecent images of a child.
The alleged victim told the court the incident took place in a flat at Grafton Close belonging to John Stingemore.
The jury has been told that he abused boys during his time as the home's manager. He was due to be tried alongside Fr McSweeney but was found dead in his home last month.
When the alleged victim was asked why he did not tell anyone at the time what had happened, he replied: "Who would I tell? There was no-one else other than the staff.
"It would only get reported to Mr Stingemore.
"I felt a bit ashamed as well."
The alleged victim also described how the priest fondled him over his clothes as he sat on his lap while playing video games, and offered to help him wash as he was having a bath.
During cross-examination, Stephen Spence, defending Fr McSweeney, put it to the man that he was not telling the truth, which he denied.
The trial, which is expected to last two weeks, was adjourned until Wednesday.

Their quartet of Marcus Hellner, Lars Nelson, Johan Olsson and Daniel Richardson led from start to finish and completed the course in one hour 28 minutes 42 seconds.
The battle for silver and bronze was won by Russia - who were watched by President Vladimir Putin.
The bronze was taken by France - their first medal in the event.
A day after their women's team came from behind to earn a narrow relay victory, Sweden's anchor Hellner skied alone for the entire fourth leg and grabbed a Swedish flag to wave as he entered the stadium and proceeded unchallenged down the final straight.
Hellner started the final leg with a 14-second lead over Russia's Maxim Vylegzhanin and quickly extended the gap, eventually winning by 27.3 seconds.
It was another disappointing day for Norway, who had fallen a minute behind by the second exchange and ended up fourth, a day after their heavily favoured women also failed to get a medal.
Chris Ashton will appeal against a 10-week ban that would rule him out of England's entire Six Nations campaign.
[NEXT_CONCEPT]
A Roman Catholic priest took photographs of a boy after sexually abusing him, a jury has been told.
[NEXT_CONCEPT]
Defending champions Sweden took gold in the men's cross country 4x10km relay at the Winter Olympics in Sochi.