Questions have been raised over Tony Blair's authority following the resignation from government of David Blunkett.

It is the second time the prime minister has seen a cabinet minister resign after being re-appointed to government following a prior scandal.

Blair faced tough questions in the Commons when he appeared before MPs, with Tory chief Michael Howard branding him a "lame duck".

The row, which will generate acres of negative headlines, comes amid growing criticism of Blair's government.

The prime minister enjoyed a burst of popularity following the Olympics bid win, the G8 summit and his handling of the London terror attacks.

But now there are doubts over whether his European presidency is making any progress on the key issues, while business group have been concerned about the government's failure to press for radical reform of public sector pension arrangements.

Resignations

Blunkett's departure from government for the second time follows the similarly turbulent career of Peter Mandelson.

In December 1998 Mandelson resigned as trade secretary after revelations about a secret £373,000 home loan from former paymaster general Geoffrey Robinson.

And in January 2001 Mandelson resigned again, this time from the post of Northern Ireland Secretary after a row over whether he helped the Hinduja brothers gain British passports.

Mandelson was later cleared of "improper" behaviour, and Blair appeared determined not to repeat this mistake a second time and sack Blunkett immediately the latest scandal broke.

But Blunkett was vulnerable after his rapid return from government in May this year following the general election.

He first resigned as home secretary last December amid a row over his private life and an affair with a married woman.

Blair's decision to bring back both Mandelson and Blunkett is a sign of his loyalty to those close to him but also indicates a lack of heavyweight allies at the top of Labour.

Authority

The cabinet reshuffle may now allow the prime minister to reassert his authority.

But it comes amid increasing signs that members of the cabinet are looking beyond Blair's premiership.

Rows over education reform and the smoking ban have made the headlines as ministers briefed against each other.

The breakdown in cabinet discipline was read as a sign that the prime minister no longer commands the respect of his colleagues.

And the loss of the work and pensions secretary deals a blow to a department preparing two major reforms supposed to be at the heart of the prime minister's third term in office.

A major report on pensions reform and a shake-up of incapacity benefit are planned for the coming weeks.

Blunkett's successor will have to deal with Number 10's calls for radical reform while also seeking cross-party consensus and dealing with Labour's backbenches.