The former Tory’s decision to stand down at the next election will deprive Westminster of one of its most interesting characters.
Mr Stewart, who ran against Boris Johnson in the latest leadership contest, also announced he would resign from the Conservative Party.
The deputy Labour leader was appearing on ITV's Wednesday evening show 'Peston' when he made the comments.
A spokesperson said Rory Stewart's remarks were in line with the British government’s stated position.
Conservative MP Rory Stewart has been elected the new chair of the House of Commons Defence Select Committee, taking over from fellow Tory James Arbuthnot.
Mr Stewart, who represents the Cumbria constituency of Penrith and The Border, has served in the army and the diplomatic service, along with running a charity in Afghanistan.
Read: Stewart: No soldier dies in vain