Seven MPs have signed an early day motion criticising Greenpeace for attempting to "blackmail" them.
The motion, started by Labour MP Nick Palmer, said the organisation had sent 7,000 emails to each of 57 MPs, causing their mailboxes to crash.
Greenpeace was trying to persuade the MPs, who had signed an EDM in October against the expansion of Heathrow Airport, to vote for a Tory motion last week.
Palmer's motion claimed Greenpeace had said it would stop the emails only if MPs committed themselves to voting as it wished. "My desire not to be blackmailed far outweighs my rejection of the third runway," he said.
Greenpeace said the messages were sent independently by its supporters.
"MPs assumed we deliberately crashed their mailboxes," said a spokesman. "In fact, we just underestimated the determination of our supporters."