Administrators said no redundancy or store closures have yet been confirmed.
Cardiff-based Peacocks operates 423 stores with 4,369 employees, while Jaeger, which was bought by Mr Day in May 2017, operates 76 stores and concessions and employs 347 people.
On Teesside, there are Peacocks outlets in Cleveland Retail Park, Castlegate Mall in Stockton, Parkway Mall in Coulby Newham and Redcar.
A Peacocks store in Captain Cook Square in Middlesbrough closed in early 2019.
The nearest Jaeger store is in Newcastle.
Mr Day’s EWM group had already placed its Edinburgh Woolen Mill and Ponden Home business under administration earlier this month.
But EWM had saved Peacocks and Jaeger more time in the hopes of finding a new buyer or investor for part or all of the business.
The High Court gave the company two more weeks to try to find a solution.
It has now passed, but FRP co-administrator Tony Wright remains optimistic about the security of their future.
“Jaeger and Peacocks are attractive brands that have endured the well-known challenges that many retailers are currently facing,” he said.
“We are in advanced talks with a number of parties and are working hard to secure a future for both companies. ”
In a statement, EWM Group said it will continue to help administrators find the best possible outcome.
He said: “In recent weeks we have had constructive discussions with a number of potential buyers for Peacocks and Jaeger Ltd, but the continued deterioration of the retail sector due to the impact of the pandemic and of the second lockdown made this process longer and more complex than we would have hoped.
“As long as these talks are underway, we no longer have the option of further extending the standstill agreement originally imposed by the High Court six weeks ago.
“Therefore, as trustees, we have made the desperately difficult decision to place Peacocks and Jaeger in the administration while these talks continue.