But the latest proposal, part of an effort to tackle the crowded international cricket schedule and save on costs, has divided players and fans, many of whom consider Tests the gold standard.
The ICC allowed four-day Tests in 2017 and they have been tried in one-off games between South Africa and Zimbabwe and England against Ireland.
But they are not allowed in the Test world championship, which is currently led by Virat Kohli's India.
The MCC Cricket Committee and MCC World Cricket Committee both believe Test cricket should continue to be played over five days.
"MCC has noted the recent discussion regarding the future of Test cricket and the ICC's desire to debate the introduction of four-day Test cricket to replace the current five-day format in the World Test Championship from 2023.
"The MCC Cricket committee and MCC World Cricket committee have recently discussed the issue and although they can see some benefits that four-day Test cricket could bring, both committees believe that Test cricket should continue to be played over five days."
The MCC, founded in 1787 and based at its ground Lord's in London, is the custodian of the laws of the game. Federation of International Cricketers' Associations executive chairman Tony Irish last week stressed there was "currently a lot of negative sentiment" concerning the four-day proposal.