Human rights groups have branded David Cameron's clampdown on law firms pursuing "spurious" claims against Iraq veterans "ill-judged and inappropriate".
In a letter to the Prime Minister, seven organisations warned Mr Cameron not to interfere in the process of investigating allegations against British troops.
The groups acknowledged that many of the claims were "as yet unproven" but they were "extremely serious" and the investigation process should be allowed to run its course.
The Prime Minister has asked the National Security Council to draw up a plan to "stamp out" what he described as an "industry" trying to profit from servicemen through "spurious" claims.
Proposals for action include measures to curb the use of "no win, no fee" arrangements and accelerate the introduction of a 12-month residence test for eligibility for legal aid.
Law firms which are found to have abused the system could also face tougher penalties under the measures being considered.
In a joint letter Freedom from Torture, Human Rights Watch, the International Commission of Jurists, FIDH, Legal Action Worldwide, Redress and Rights Watch (UK) expressed their "serious concern" about statements by Mr Cameron and Defence Secretary Michael Fallon.
They said the Iraq Historical Allegations Team (Ihat) was investigating serious claims, including of war crimes, and should not come under political pressure.
"While many of these allegations are as yet unproven, they are extremely serious and surely require that you, the Ministry of Defence (MoD) and other parts of Government avoid any real or perceived interference with the investigative process," the groups told Mr Cameron.
"To say, as you did, that the 'National Security Council will draw up a plan to stamp out this industry' could be construed as an executive comment on the strength or weakness of any particular allegation."
The groups added that Mr Cameron's claims that service personnel were being "hounded" by lawyers over unfounded claims "ignores the fact that some very serious crimes involving the UK army in Iraq have been exposed, such as the killing of Baha Mousa".
Freedom from Torture's Sonya Sceats said: "It is deeply irresponsible for the Prime Minister and Defence Secretary to publicly denigrate allegations of torture and other serious allegations against British military personnel while formal investigations are still under way.
"Their statements risk torpedoing the Ihat process put in place by the Government itself to explore evidence that the British armed forces abused detainees in Iraq. The Ministry of Defence has already paid more than £20 million to settle 326 cases, a fact which speaks volumes about the gravity of these issues."