A row has broken out over the status of Tony Blair's pledge to slash the number of asylum seekers coming to Britain.

Apparent differences between the Home Office and Number 10 have prompted opposition politicians to condemn "muddle" and "confusion" over a key policy issue.

In an interview on Friday the prime minister said the most effective way of tackling the asylum problem was "to stop the numbers coming in".

"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.

Reports on Sunday suggested David Blunkett views the prime minister's pledge as "undeliverable".

The home secretary saw Blair's statement as "a direction not a target" according to the paper.

The latest row comes as the asylum issue continues to cause difficulties for the government.

Figures out later this month are expected to show that last year the number of asylum seekers topped 100,000 for the first time.

The Home Office confirmed the prime minister's target was "a longer term objective for years to come".

"The prime minister was highlighting progress that we expect to make as a result of the measures in the Nationality Immigration and Asylum Act and that we have said all along that once the Act starts to kick in then we would expect to see reductions and those would be measured and assessed," said a spokesman.

"The prime minister said the halving of the applications was a longer term objective for years to come. It is an indicator of progress rather than a target as such."

Shadow home secretary Oliver Letwin criticised the splits between Number 10 and the Home Office.

"There is now a state of complete confusion. Does the government have a target or a commitment to reduce asylum applications by half by September or not?" he asked.

"It is entirely unclear whether the stream of recent leaks and vague statements mean that the prime minister and the home secretary now agree with us, that the medium term solution needs to be a complete change in the system, with quotas for genuine refugees instead of on shore asylum applications.

"Do they now recognize - as we made clear in our recent statement - that this is going to require either renegotiating the Geneva convention, the New York protocol and the Dublin convention, or failing that, withdrawing from these agreements?"

And Liberal Democrat spokesman Simon Hughes said that "everybody can see the muddle the government is in over asylum".

He said ministers should concentrate on establishing "a sane system for the whole of Europe which processes asylum claims fairly, deals with them speedily and returns those who fail in an effective and intelligent way".

"The more we try to make Britain look tough but fail to deliver, the more we lose credibility at home and abroad," Hughes warned.

"We should be setting examples and leading the way to the international solution, not responding to short-term populist pressure."