Controversial anti-terrorism legislation will alienate British Muslims by making it a crime to defend "political violence", an MP has said.
Richard Burden ( Lab Northfield) said new laws designed to prevent people encouraging terrorism risked "making things worse".
The Government's Terrorism Bill will be debated in the Commons today and tomorrow.
It includes a range of controversial measures, including allowing suspects to be held for up to 90 days without charge.
Mr Burden said he was concerned about measures to outlaw "glorifying" terrorism. The Bill follows the London bombings in July.
The MP, who chairs the Britain-Palestine All Party Group in Parliament, is one of the main critics of the anti-terror legislation on the Labour benches.
He has argued that British Muslims who support Palestinian violence aimed at Israel could be targeted by the legislation, adding to a sense of injustice and double standards because people who defended Israel would not be prosecuted.
But Mr Burden has also come under fire from some of his Labour colleagues, who have accused him of defending terrorists such as suicide bombers. He said: "I condemn anyone who advocates the blowing up of buses or any attack on civilians. The Bill, however, does not just include such acts but any act of political violence.
"As I said, I am worried that someone could be locked up for suggesting that Palestinian political violence is justified."
He added: "I am not condoning in any way the use of terrorist violence in the West Bank or Gaza. Indeed, I spend a great deal of time arguing with people who do so because I think that such arguments are a worthwhile exercise.
"I am told that conversations that others and I have had may have played a part, albeit a small one, in helping to achieve certain ceasefires.
"But what the Bill tells me is that there is no place for that kind of dialogue. It asks me as a legislator to criminalise someone not for committing the act of violence, but for offering an opinion that may seek to justify it. By banning things or outlawing them, one will not necessarily stop them."
He added: "Criminalising a young British Muslim simply for expressing sympathy with Palestinian groups which attack Israeli settlers in the occupied West Bank will neither change his mind nor stop those attacks happening."
Last week 16 Labour MPs voted against the Bill, including former Cabinet minister Clare Short (Lab Ladywood). Measures allowing police to hold suspects for 90 days without charge have been defended by a senior Scotland Yard officer.
Assistant Commissioner Andy Hayman said counter terrorism investigations must not be hampered by the " premature guillotine" which prevents suspects being held for more than two weeks.