"It is my intention to publicly apologise to Amy Rayner and to anyone else I have offended," said Newell.
"My comments were ill-timed and they were out of order."
Luton Town have reprimanded Newell and he keeps his job.
A club statement reads
“Representatives of the board of directors of Luton Town Football Club met with the club's manager, Mike Newell, to discuss the comments made by him in the post-match press conference at last Saturday's game,” the statement said. “The club disassociates itself totally with the comments he made regarding the assistant referee, which are completely unacceptable to the club and have accepted the manager's explanation and his subsequent public apology.
“The manager was also asked to explain his comments about the board and he has accepted that his remarks were totally inappropriate. The board have severely reprimanded Mike Newell for the comments made and have warned him that any repetition of such conduct will not be tolerated. The manager gave the necessary assurances and apologised for the comments he made and would like to thank the board for its support and understanding on this matter.”