The opposition has attacked ministers after it emerged that an overhaul of emergency civil defence plans has been delayed.

According to media reports, proposals for an extensive shake-up of 55-year-old emergency planning laws will not now be published until the summer.

Shadow home secretary Oliver Letwin said ministers were failing to respond seriously to the increased terror threat.

"It is astonishing that the government is continuing to stall over the introduction of much-needed civil contingencies legislation," he said.

"Nearly 18 months have passed since the September 11 atrocities, yet we continue to see a muddled and amateurish approach to the terrorist threat."

Bruce George, chairman of the defence select committee, said it was unlikely that new legislation will be included in this autumn's Queen's Speech.

"Now we are in a situation that we are not certain if it will be in the Queen's Speech next year. It will be two years since 9/11," he said.

"The government will have to explain to the defence committee what is the reason for this elongated process."

The intervention came on the day that experts warned that the government had failed to put in place the safeguards needed since September 11.

They warned that security had not been thought through at key targets such as nuclear power plants.

Professor David Alexander, a disaster expert at the Royal Military College of Science, said the government had been too slow to respond to the increased threat of an attack.

"There is no doubt whatsoever that September 11 was a wake-up call for the emergency services and the process of emergency planning," he said.

"Since September 11, I don't think progress has really been rapid enough. Emergencies and disasters are now blipping away on the government's radar screen and something has to be done."

"With Britain effectively on a war footing, it is critically important that the government sharpens up its act."