David Cameron has urged Tory MPs to take a stand on fighting terror on the eve of a vote in Parliament on authorising UK airstrikes in Syria.
The prime minister called on them not to "sit on their hands" and side with Jeremy Corbyn and others he labelled "a bunch of terrorist sympathisers".
Labour's leader has said bombing is not a sensible way to bring peace to Syria.
Opposition leader Mr Corbyn was forced to offer a free vote to his MPs after a shadow cabinet rebellion.
As many as 50 Labour MPs could support David Cameron although party sources have suggested this number is falling as Mr Corbyn seeks to persuade them to listen to his arguments against intervention.
Meanwhile, thousands of protesters, led by the Stop the War coalition, have taken to the streets of London for the second time in four days to protest against bombing.