Armitage, 28, was suspended from the England Saxons elite player squad after being arrested on suspicion of assault, the Rugby Football Union said.
London Irish back Armitage was detained by Devon and Cornwall Police following an incident in a nightclub early on January 29, according to an RFU statement. He was later released on bail.
Armitage, who has won 26 caps, started at full-back when England Saxons beat the Irish Wolfhounds 23-17 in Exeter on Saturday.
In a statement, the RFU said Armitage had been detained by Devon and Cornwall Police early yesterday.
The RFU said: “The London Irish full-back was released from the England Saxons camp following the international match against the Ireland Wolfhounds on January 28.
“He was later arrested in Torquay on suspicion of assault following an altercation in a nightclub, interviewed and was then released on police bail while inquiries continue.”
A police statement said: “A local man received a split lip during the incident but did not require medical treatment.”
England’s interim coach Stuart Lancaster said: “We take issues surrounding the behaviour of England players very seriously, and as such have decided to suspend Delon from the Saxons EPS pending the result of the police inquiry.
“We will then consider if further action is appropriate under the EPS code of conduct. High standards of behaviour are required from England players on and off the field.”