Colin Sampson has written to councillors in Yeovil, Somerset, to complain about an official he claims walked in saying: "You've had your 20 minutes".
Mr Sampson, 50, said the "extremely distressing" interruption prompted his father and other mourners to leave the funeral of Gwen Sampson early.
Yeovil town council has promised an inquiry into the allegations.
Minutes late
Mr Sampson, from Winscombe in Somerset, said the funeral of the 73-year-old was ending with a piece of music by Elgar when the doors were thrown open.
"He (the official) just stood and bellowed at the Reverend 'You are out of time, everyone will have to leave the room'.
"The Reverend pleaded with him to let everybody stay until the music had finished, but he said, 'You've had your 20 minutes, you know that you are only allowed 20 minutes, everybody has got to leave the room now.'"
Mr Sampson says the funeral had only overrun by five minutes and the next service was not due for another half an hour.
He says the official walked past his mother's coffin and left the chapel, but then returned and repeated his demands.
He also alleges the official "stood over him" as he paid his last respects at his mother's coffin.
Tearful mourners
Mr Sampson added: "It was extremely distressing.
"Most people left the room in tears not because my mother had died, but because the funeral had been desecrated."
Chairwoman of Yeovil's crematorium and cemetery committee Ruth Kendall said she had received letters from Mrs Sampson's family and the clergyman.
She has now arranged a meeting on Monday with the official who has worked at the site for 10 years.
She said his actions were "completely out of character".