Gordon Brown has claimed that the 100,000 civil service job cuts announced in his spending review are achievable without hitting frontline services.

The comments came amid growing union anger at the proposed cull of public servants.

The chancellor insisted that the cuts, allied to cost savings, will be delivered without reducing service provision.

"New technology enables things that used to be done manually to be done electronically," the chancellor told the BBC on Tuesday.

Responding to criticism from unions and some Labour MPs he told staff to "think again" before taking strike action.

"We will not be diverted from what's got to be done," Brown said.

In his spending review Brown kicked off the general election campaign with a pledge to deliver "substantial extra resources" for frontline services.

Implementation of the Gershon review of Whitehall, he said, would lead to £21 billion in savings - allowing cash to be spent in areas such as education and health.

Despite the cuts, Brown insisted he would deliver "more investment not less, now and into the next parliament".

Brown said the civil service was set to face a substantial "rationalisation and relocation".

Any future civil service jobs would be based on "a presumption in favour of location in the regions".

And he warned that the culture of sick leave within the civil service would be tackled by a revamp of the system of self-certification.

He said the overhaul would be "ambitious" but was necessary to deliver more cash for frontline public services.

The chancellor also told MPs he planned to implement a substantial sell-off of government assets and land – yielding £30 billion over the next four years.