Justice Secretary Chris Grayling has called for an "immediate examination" of the legal aid system after it emerged terror suspect Abu Hamza's legal battles cost taxpayers almost £1 million.
"Resources aren't limitless" and should be reserved for cases where there is genuine need, Mr Grayling said.
Questioning whether the system provided value for money, the Cabinet minister spoke out after taxpayers were left with a total bill of more than £900,000 for cases involving the radical cleric.
It also emerged that Jordanian terror suspect Abu Qatada, who is still fighting against deportation with a senior immigration judge set to rule on the case this month, has cost the taxpayer £390,000 in legal aid.
But the Legal Services Commission has secured frozen assets of £217,286.57 for use towards Qatada's bill.
Mr Grayling said: "We must never lose sight of the fact that legal aid is paid for by the taxpayer. The total costs in some cases seem very high and many - myself included - will question whether they provide value for money."
He went on: "I am concerned about public confidence in the legal aid system. I have ordered an immediate examination of aspects of the system that affect its credibility with the public. Legal aid is a fundamental part of our legal system, but resources aren't limitless. Legal aid should be reserved for cases where there is genuine need."
Hamza, who denies terror charges in New York after being kicked out of the UK following a failed appeal against extradition last month, benefited from almost £680,000 in legal aid, figures released to the Daily Mail following a request under the Freedom of Information Act showed.
This included £445,452.65 to defend him against charges of inciting terrorism, £165,460.81 fighting against extradition and £68,107.33 to fight attempts by the Home Office to remove his passport.
Home Office lawyers, who were fighting to put him on a plane, cost an additional £250,000 in legal aid, taking the total to £909,423.70