A Tory MP has written to the Met Police to ask to investigate whether Liberal Democrat David Ward committed "the encouragement of terrorism" with his Gaza tweet.
Nadhim Zahawi has asked Sir Bernard Hogan-Howe to investigate the comments.
Bradford East MP Ward was heavily criticised after saying he would "probably" fire a rocket into Israel if he lived in Gaza on Twitter.
The Lib Dems have said they have "utterly condemned" his remarks and are treating the incident as a disciplinary issue.
"Mr Ward made a number of comments about the ongoing conflict in Gaza. Tragically the most recent flare up has caused death on both sides," wrote Zahawi.
"However, Mr Ward went on to suggest that if he lived in the region, he would wish to contribute to the violence saying he would "probably fire a rocket".
"Mr Ward's tweets would appear to be prima facie evidence that he has committed the offence of the encouragement of terrorism as defined by Section 1 (2) of the Terrorism Act 2006."
Zahawi concluded the letter by saying he hoped police would investigate this matter "with a matter of urgency".
Ward defended his tweets and said he condemned the violence on both sides of the Gaza conflict. He told Radio 5 Live: "The comment was about understanding why people are firing rockets. I am not condoning that.
"In fact, yesterday in the House of Commons I condemned it. I'm saying I understand why people are so desperate that they are doing it."
"They are doing it because they are absolutely desperate and politicians in the West are failing them," he added.
The comments arrived a year after Ward was suspended from the party for two months after tweeting on the same subject.
That time, he refused to apologise after asking how long the "apartheid state of Israel" can last and suggesting "Zionists" are "losing the battle".
His latest remarks have been described as "vile" by the Labour Party in a tweet, with Conservative Party chairman Grant Shapps saying his comments were "appalling".
A Lib Dem spokesperson said: "Nick Clegg has been at the forefront of calling for peace in Israel and Gaza.
"We utterly condemn David Ward's comments, they are not representative of the Liberal Democrats.
"The party takes this matter very seriously."