John Reid has admitted he has no exact figures for the number of illegal immigrants in the country, prompting claims that the government is "incompetent".

The home secretary said the government had inherited a legacy of an unknown number of illegal immigrants from previous administrations and such people were leading secretive lives.

However he insisted that the government has met its long-standing targets to deport more failed asylum seekers.

Speaking to BBC Breakfast, Reid said the number of false asylum seekers coming into Britain was "now being dealt with quicker than ever".

"I hope that the figures out soon will show that we have met our objective of removing more false asylum seekers in this country than are coming in," he added.

Reid's comments came after the civil servant in charge of deporting illegal immigrants told a committee of MPs he did not have "the faintest idea" how many were living in Britain.

Dave Roberts, director of enforcement and removals at the Immigration and Nationality Directorate, was giving evidence to the Commons home affairs committee.

He also said those who overstayed illegally were not pursued as "individuals" as this was "not an effective strategy".

"We are making huge efforts to remove them but not at the basis of tracing individuals," Roberts said.

The home secretary said the number of failed asylum seekers being deported was running at about 1,000 a month.

Full details of deportation targets are due to be published next week.

Reid went on to acknowledge "there are some things we don't know".

"We don't know the number of illegal immigrants hiding in this country, partly because we do not know how many we have inherited in the past generation."

He added that the paper-based system which kept track of people leaving the country had been abolished under the previous government.

"We are not going to be able to solve this until we have biometric passports and ID cards counting those who leave," he said.

Commenting on the row, Liberal Democrat home affairs spokesman Nick Clegg said: "This breathtaking admission confirms what many people have suspected for some time: the government's management of our immigration system is completely incompetent.

"The Liberal Democrats have long argued that a firm and fair immigration system can only be established if the day-to-day running of the system is removed from the Home Office."