Beverley Hughes has resigned as immigration minister following revelations that she was warned about immigration abuse last March.

The minister has been under pressure for weeks following claims she failed to act on warnings of a scam concerning work visas from eastern Europe.

Hughes met the prime minister this morning - following fresh accusations that she was warned in writing about immigration abuse by then junior Home Office minister Bob Ainsworth as early as March 4 last year.

Addressing the media Tony Blair denied he is taking personal charge of immigration in the wake of the crisis but has called for swift action against "systematic fraud".

Statement

In a Commons statement Hughes defended her actions over weeks of "sustained parliamentary and media criticism".

"I have done my best to answer whatever questions I have faced honestly," she said.

"I am proud of what I have achieved over the last two years."

The former minister said she had "unwittingly" given a misleading account when she appeared on the BBC's Newsnight programme on Monday.

"I realised that what I said then was not fully consistent with the correspondence," she said.

Suggesting there was a "special obligation" on ministers dealing with immigration, Hughes added: "I cannot in conscience continue as immigration minister."

Praise

Home secretary David Blunkett said Hughes was a "highly able, honest, competent minister" who had faced "weeks of vitriol" at the hands of the media.

Meanwhile Downing Street has announced that Des Browne, the work minister, is to replace Hughes at the Home Office.

The Tories have called for a full investigation into the immigration crisis - demanding to know why it has taken so long to get to the facts.

"Why has it taken so long and why did the government not tell the truth from the start?" said shadow home secretary David Davis.

"Her resignation will not solve the crisis, nor will more gimmicks from Downing Street, such as the prime minister taking personal control of yet another area of policy.

"What is needed now is a proper, full independent investigation into this crisis, which will report urgently. It must be established without delay."

Liberal Democrat leader Charles Kennedy said a “resignation in itself” would not get to the bottom of the situation and repeated his demand for a wider inquiry.

Blair press conference

The resignation came ahead of Tony Blair's appearance before the media at midday.

Blair rejected reports that he has taken "personal charge" of immigration - but added that he would take "a close interest" in the current situation.

He warned that the current problems concerning applicants from EU accession states "should not colour the whole picture".

"I think what we really need to do is to take swift action... if there are problems from Bulgaria and Romania," said the prime minister.

Blair said Hughes had done a "fantastic job" and had "behaved with integrity in coming forward" when inconsistencies between her public statements and private correspondence emerged.

"There are difficult situations for people who are ministers and I think she has shown a great deal of courage," he added.

It is not known whether Hughes formally resigned or was forced to quit by Number 10.

Downing Street said she resigned after giving a "misleading impression - albeit unwittingly" to parliament.

It is thought that the Ainsworth letter made it impossible for her to remain in office.

Ignored

Hughes stands accused of repeatedly ignoring warnings that the work visa system was being abused by immigrants from Romania and Bulgaria.

She may also be guilty of misleading MPs over the details of when she became aware of fears over visa fraud - which is a resignation issue in itself.