Peter Mandelson has denied that New Labour is in decline and warned critics not to underestimate Tony Blair.

The former Northern Ireland secretary and close ally of the prime minister wrote in the Spectator magazine this week that so-called "wobbles" are nothing compared to previous Labour or Tory governments.

"By comparison with summers past, this government is not having a particularly rough time," the Hartlepool MP said.

"Media hyperbole" has been responsible for many of the damaging headlines and press comment in recent weeks concerning allegations of duplicity over Iraq and drift in domestic policy, Mandelson argued.

"Alastair Campbell's comfortable survival at the hands of his inquisitors yesterday exposed the synthetic nature of the rage directed against the government," he wrote.

"Those with long memories and perspective know that we are light years away from the storms that used to rock Mrs Thatcher's ship and the internal battles that tore apart John Major's administration."

This "does not mean that everything has gone perfectly well", the two-time former Cabinet member conceded.

The man who did more than anyone else to shape Blair's communications strategy admits that media gaffes have been "magnified because of New Labour's legendary prowess in this area".

"But tiredness should not be confused with terminal 'decay', as some BBC political correspondents suggest," he contends.

"The nagging feeling that the New Labour 'project' has lost momentum is because too few in government talk publicly and convincingly about their mission, rather than that its purpose no longer exists."

Policy needs to be re-energised, but not radically re-thought, Mandelson believes.

And he insisted "the government has the self-confidence and firepower to renew itself".

Mandelson suggested that reform of schools, hospitals, transport and the criminal justice system should go further.

This will happen, he argued, because the "underlying tectonic plates" of politics remain in Labour's favour.

And above all the prime minister himself is far from finished, his friend predicted.

"Tony Blair's determination should never be underestimated," he concluded.