Getwestlondon has seen an email from London North West Healthcare NHS Trust (LNWH), sent on January 5, to staff at Ealing, Northwick Park and Central Middlesex Hospitals and other community services.
The email asks employees to release 100 extra beds through "expediting patient discharges" over the following two days from the date the email was sent.
Staff were instructed to do this by discharging 130 patients from Northwick Park and 65 at Ealing Hospital, which LNWH said was a 30% increase in "best discharge levels".
Central Middlesex and other community services under the trust were made aware of the target but were not given an exact number to discharge, LNWH said.
The email was met with anger from Oliver New, chairman of campaign group Ealing Save Our NHS.
He said: "NHS North West London should admit their policies are wrong, and restore the much needed A&Es at Central Middlesex and Hammersmith Hospitals.
"They should also re-open A&E facilities for children at Ealing.
"All of those A&Es were there because they were needed and they are still needed today."
A spokesman for LNWH said the email was a response to pressure faced in late December last year and early January this year.
The instruction was a regular practice across hospitals and was done so safely, the spokesman said, who added LNWH came "very close" to the target.
The spokesman said: "This type of operational communication with our staff is an appropriate and timely response to the additional pressures on our services over the Christmas and New Year period.
"Patients are never sent home earlier than they should be. They are discharged in a safe and timely manner that is appropriate for them.
"Like other hospitals across the country, we are facing additional pressures on our services.
"Despite this, our hospital and community staff continue to do an outstanding job ensuring patients receive high quality care in a safe environment."
The spokesman said the situation was "challenging at this time of year" but not "unique".
According to LNWH NHS, 420 more patients attended Emergency Departments and Urgent Care Centres between December 26, 2016, and January 4, 2017, compared to the same period a year before.
It comes after getwestlondon revealed the number of patients spending at least 12 hours at LNWH hospitals had soared 324% from 1,706 attendances in 2011/12 to 7,236 in 2015/16.
Keep up to date with the latest news in west London via the free getwestlondon app.
You can even set it to receive push notifications for all the breaking news in your area.