The treatment of foreigners seeking asylum in Britain was criticised on Thursday as being inhumane and falling below acceptable standards.

The Independent Asylum Commission said the government is denying sanctuary to those who genuinely need it, while not being firm enough in returning those whose claims are refused.

"The UK asylum system ... is marred by inhumanity in its treatment of the vulnerable," said the commission, a committee including senior politicians, lawyers and church leaders.

The government rejected the claims, saying Britain operates a firm but humane system.

The commission said it had collected evidence from hundreds of individuals and organisations. It said the asylum system has improved but is not yet "fit for purpose".

"The treatment of asylum seekers falls seriously below the standards to be expected of a humane and civilised society," said Lord David Ramsbotham, a former chief inspector of prisons and member of the commission.

"The enforced destitution of many thousands of refused asylum seekers is indefensible and runs the risk of placing a shameful blemish on our nation's proud record of providing for those who come here in search of sanctuary," he added.

A counselling centre in Somerset told the commission that survivors of torture overseas are often given an unsympathetic reception by officials.

"We are frequently dismayed by the apparent stance of the Home Office in assuming that our clients are lying to gain asylum," said the Bath Centre for Psychotherapy and Counselling.

"Feelings of shame are prevalent among people who have been tortured, particularly if this involved their sexual organs. Having to air this as part of an asylum claim is very distressing."

Numbers seeking asylum in Britain have fallen to around 23,000 a year, down from a peak of nearly 85,000 in 2002, when the high numbers forced the issue to the top of the political agenda.

The government said Britain has a "proud tradition" of offering sanctuary to those who need protection.

"The claims made in this report are not based on any thorough knowledge," said Lin Homer, chief executive of the government's Border and Immigration Agency.

"I totally refute any suggestion that we treat asylum applicants without care and compassion.

"We operate a firm but humane system, supporting those who are vulnerable with accommodation and assistance."