The Conservatives have slammed the government's record on dealing with asylum seekers.

Party leader Iain Duncan Smith used a BBC interview to describe the handling of the problem as "appalling".

His attack followed reports that figures to be released at the end of February will show the number of asylum seekers has topped 100,000-a-year for the first time.

Duncan Smith lambasted a pledge by the prime minister to halve the number of asylum seekers by September, saying it was an ineffective gesture.

"This is too little, too late. Right now it's just promises and targets from a government that has failed endlessly to meets its promises," he said.

"What he has to do is to say that we will only take certain quotas. When he does that, that will be about taking real action."

Shadow home secretary Oliver Letwin followed up the salvo with a call for radical action that went beyond David Blunkett's decision to extend the asylum "white list"."This means changing or withdrawing from international agreements and bringing in a quota-based system for genuine refugees so that there is no more asylum seeking within Britain itself," he said.

Tony Blair, in his second TV grilling in as many days, said there was a simple solution to the problem.

"The only way of dealing with this is to stop the numbers coming in," the prime minister said.

"Once people get in, unless you can discover what country they come from and get that country to agree to take them back, then it is very difficult to get them back."

Blair also warned that groups such as the BNP would exploit the issue "for the wrong reasons" if action was not taken.

"I would like to see us reduce it by 30 or 40 per cent in the next few months and I think by September we should have it halved," he said.

The figures should go below 45,000 "in years to come" Blair added.