The government is being urged to rethink planned restrictions - due to come in within days - on legal aid for asylum seekers in England and Wales.
Many failed asylum seekers are held in detention ahead of deportation
MPs fear plans to pay solicitors after they complete immigration and asylum appeals, and often only if they win, could mean genuine cases are not heard.
The all-party Constitutional Affairs Committee said the aim of limiting the unworthy appeals was "laudable".
But chairman Alan Beith said the plans went too far in the other direction.
Few solicitors or refugee groups would want to take on cases if there was a clear chance they would not be paid, Mr Beith said.
This could happen even if the appeal was considered by a judge to have merit, he added.
"Discouraging solicitors and barristers from taking on all but the most cast-iron cases could amount to a serious denial of justice."
This could mean that those wrongly denied justice could face death or torture on return to their home countries.
The government should not use the legal aid system to restrict legitimate appeals, he added.
"The government must re-think its position."
The legal aid reforms are due to come into force on 4 April.
Three major reforms of the asylum and immigration system have been undertaken over the past few years.
Earlier plans to end courts' jurisdiction on asylum and immigration tribunal cases were criticised by the committee as "without precedent".
MPs called for judicial oversight to be maintained.