London Irish filed for administration on Wednesday following their suspension from all club competitions over a failure to provide financial assurances.
The Rugby Football Union on Tuesday confirmed that neither Irish's owner Mick Crossan nor the American consortium planning to buy the club were able to prove they had the finances to compete in the English Premiership for the 2023/24 campaign.
Crossan has revealed that entering administration was the only choice left after the suspension ended any chance of the prospective takeover going through.
"This decision has ultimately ended any hope of an acquisition of the club and has regrettably forced us to file for administration this morning (Wednesday)," he said.
"Administration has always been the last resort and something we hoped we could avoid. And we bitterly regret the difficulties it will present to each and every one of you.
"My focus is now on working with the appointed administrator and I hope that the club will come out of administration as quickly as possible."
London Irish are the third English Premiership club to collapse this season after Wasps and Worcester became casualties of the financial crisis gripping the top-flight.
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