Britain is spending more than £70 million a year to support failed asylum seekers, the Government has revealed.
The figure was disclosed by the Home Office as it set out details of proposals to slash benefits for those who remain in the country illegally.
Taxpayer-funded help - normally for accommodation and a weekly cash allowance to cover essential living costs - was being provided to an estimated 15,000 failed asylum seekers and their dependants in March, according to the department.
It added: " In 2014-15, such support cost an estimated £73 million."
The sum is made up as follows:
:: An estimated £28 million for around 4,900 failed asylum seekers who "would otherwise be destitute" and who meet certain conditions, such as a medical reason why they cannot travel or if they have made submissions to the Home Office which are outstanding.
:: An estimated £45 million for around 2,900 families. The current law allows help to continue after asylum claims are exhausted if the applicant has a dependent child.
Planned changes to rules governing taxpayer support for failed asylum seekers were trailed at the weekend as the Government struggled to get a grip on the Calais migrant crisis.
At present, migrants can obtain accommodation and a £36-a-week allowance from the moment they claim asylum in the UK, but support continues to be given to thousands after their claim has failed.
Setting out its proposals today, the Home Office said the system established in legislation introduced 16 years ago is now being used "in large measure" to support failed asylum seekers.
It said: "This is wrong in principle and sends entirely the wrong message to those migrants who do not require our protection but who may seek to come to or remain in the UK in an attempt to benefit from the support arrangements we have put in place for those who need our protection.
"Failed asylum seekers are illegal migrants and are no more deserving of welfare support than any other migrant in the UK unlawfully."
Under the plans, support for failed asylum seekers who make no effort leave the UK at the point their claim is finally rejected will be closed off.
Help may still be given in cases where there is a "genuine obstacle" preventing return to a home country.
Parents, guardians or others with dependent children will no longer be classed as "asylum seekers" after their claim is rejected for the purposes of assessing their eligibility for support.
Instead, a similar approach will be adopted to the one currently used for failed asylum seekers without children under 18 - meaning their entitlement to help will end after a grace period of at least 28 days after their claim is finally rejected.
The Home Office said the current scenario is "unsatisfactory" adding: "It creates an incentive to remain in the UK unlawfully. It provides no incentive to comply with the law. Failed asylum seekers should be expected to leave the UK where it is possible for them to do so.
"We are otherwise providing a forum of public subsidy for illegal migrants who could and should leave the UK. This should end."
The Government insisted safeguards for children would be retained under the reforms.
Support would continue to be available to families when there is a "practical obstacle" to their departure from the UK which is beyond their control, while the grace period could be extended in some circumstances.
Judith Dennis, of the charity Refugee Council, said: "The Government is so keen to appear tough it's now viciously targeting vulnerable families and appears determined to take away people's ability to feed, clothe and house their children, without any independent oversight.
"There is no evidence that introducing new, cruel policies which could leave children sleeping on the streets will convince families to return to their countries of origin where they believe their lives are at risk."