Charles Clarke, the Home Secretary, made the admission as he came under fire over the broad wording of the Terrorism Bill, which outlaws the glorification of terrorist attacks.
"It's not targeted at supporters of this type of extremism, but I certainly think animal terrorism is something that needs to be attacked," he told the joint committee on human rights.
"Those who argue that committing violent acts to promote the case of animal rights and justifies it with phrases such as 'violence begets violence' ... would be covered by this Act."
Mr Clarke was accused yesterday of threatening basic human rights and undermining the constitution through his plans for a national identity card scheme.
Two parliamentary committees have denounced the plans. The Lords committee on the constitution proposed creating an independent commission to run an ID Card to take the system out of direct Government control. A report by the committee called for safeguards "to protect individuals from excessive intrusion into their affairs by institutions of the state or indeed by others".
It said: "This is all the more important when the scheme envisaged will record in a single database more information than has ever been considered necessary or attempted previously in the United Kingdom or in any other Western country."
In a separate report, the Joint Committee on Human Rights said: "It is not clear that the gathering of personal information of persons applying for a passport, for example, bears any relation to the protection of national security or the prevention of crime."
The Government looks doomed to defeat in the House of Lords today over plans to create a fresh offence of inciting religious hatred.
The proposal had been defeated by peers but was reintroduced after the election by Ministers who argue it gives Islam the same legal protection enjoyed by other faiths.
Peers of all parties, supported by comedians and entertainers, have condemned the proposals as an attack on free speech. Critics will today attempt to amend the Racial and Religious Hatred Bill by setting restrictions on when prosecutions can be mounted. It will stipulate that no one can be found guilty of the new offence unless it can be proved they intended to stir up hatred. Nor could they be prosecuted if it could be shown they were exercising freedom of speech.
Ministers are also braced for attacks from Labour MPs tomorrow over the Bill, which proposes detention without charge of terrorist suspects for up to three months.
At least 20 members of the left-wing Campaign Group are expected to rebel. A spokesman said: "There is concern on the backbenches that fundamental civil liberties won over generations could be undermined." Shami Chakrabarti, director of the civil rights lobby group Liberty, said: "The bill now faces opposition from the Commons and the Lords despite the Government's best efforts to make the bitter pill palatable. Whether it's the impact on race relations, the expense, the invasion of privacy or government IT fallibility, more people are recognising that this bill cannot go forward."