The phrase "to defy the whip" refers to resisting or refusing to follow orders or instructions from someone in a position of authority or control. Full definition
There were 52 Conservative MPs who took part in the rebellion over House of Lords reform and the EU referendum, while there were only six Labour MPs who defied the whips over both major votes. (totalpolitics.com)
Rather, the most eyecatching of their number was former defence secretary Liam Fox, who defied the whips for the first time in his 23 - year parliamentary career. (totalpolitics.com)
But then he needs to appreciate that some of the issues on which the 2010 — 15 Tory rebels defied the whip were rooted in 2010 manifesto pledges, a document that included the words, «We will ensure that by law no future government can hand over areas of power to the EU or join the Euro without a referendum of the British people.» (blog.politics.ox.ac.uk)