A proposed change in immigration law that could see legitimate asylum claims blocked for up to a decade, has prompted a furious response from politicians and human rights groups.

The new rules, due to come into force in the autumn, will mean that anyone deported from the UK will be barred from claiming asylum in this country for 10 years, regardless of how much their circumstances change. The legislation has obvious implications for the hundreds of failed Zimbabwean asylum-seekers living in the UK who are now facing return to the crisis-hit country.

The Liberal Democrats' justice spokesman Chris Huhne said: "As drafted, these rules are offensive in principle and also probably contravene basic human rights law. It's simply inhuman to insist that someone needs to wait up to 10 years to reapply for UK residency if they have dependants in the UK or if they are deported to a dangerous country like Zimbabwe."

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Under the new law, any immigrant or asylum-seeker who is forcibly removed from the country will be banned for 10 years from re-entering the UK. For those who leave voluntarily the ban will be between one and five years. Until now re-entry following deportation was up to the discretion of immigration officers, which allowed for exceptions to be made on grounds of asylum.

The law was originally due to be implemented on 1 April. However, following concerted lobbying from MPs, this has been pushed back to 1 October, to allow those staying in the UK illegally an extended period to leave voluntarily.

The Liberal Democrat peer Lord Avebury said the move was "part of a government attack on existing migrants", adding that there would be an appeal against the law on human rights grounds. "What's so objectionable is that the same penalties are exacted on everyone," he said.

"Of course Zimbabweans won't voluntarily go back. If any of the 1,000 Zimbabweans who are now threatened with deportation goes back and gets persecuted, they'll be stuck because of this 10-year ban."

A Refugee Council spokeswoman said such legislation went against the country's duty to aid those fleeing persecution. "The UK is a signatory to the Refugee Convention, and as such has an obligation to protect people who are fleeing for their lives", she said.